Sample records for heat pipe nuclear

This project was devoted to a preliminary assessment of the feasibility of designing an Encapsulated NuclearHeat Source (ENHS) reactor to have a solid core from which heat is removed by liquid-metal heatpipes (HP).

National Aeronautics and Space Administration — This Small Business Innovation Research Phase I project will develop titanium Loop HeatPipes (LHPs) that can be used in low-mass space nuclear radiators, such as...

It is approximately 10 years since the Third Edition of HeatPipes was published and the text is now established as the standard work on the subject. This new edition has been extensively updated, with revisions to most chapters. The introduction of new working fluids and extended life test data have been taken into account in chapter 3. A number of new types of heatpipes have become popular, and others have proved less effective. This is reflected in the contents of chapter 5. Heatpipes are employed in a wide range of applications, including electronics cooling, diecasting and injection mo

A comprehensive, up-to-date coverage of the theory, design and manufacture of heatpipes and their applications. This latest edition has been thoroughly revised, up-dated and expanded to give an in-depth coverage of the new developments in the field. Significant new material has been added to all the chapters and the applications section has been totally rewritten to ensure that topical and important applications are appropriately emphasised. The bibliography has been considerably enlarged to incorporate much valuable new information. Thus readers of the previous edition, which has established

To evaluate the concept of the cooling device, 2-step CFD analysis was conducted for the cooling performance of hybrid heatpipe, which consists of single fuel assembly model and full scope dry cask model. As a passive cooling device of the metal cask for dry storage of spent nuclear fuel, hybrid heatpipe was applied to DPC developed in Korea. Hybrid heatpipe is the heatpipe containing neutron absorber can be used as a passive cooling in nuclear application with both decay heat removal and control the reactivity. In this study, 2-step CFD analysis was performed to find to evaluate the heatpipe-based passive cooling system for the application to the dry cask. Only spent fuel pool cannot satisfy the demands for high burnup fuel and large amount of spent fuel. Therefore, it is necessary to prepare supplement of the storage facilities. As one of the candidate of another type of storage, dry storage method have been preferred due to its good expansibility of storage capacity and easy long-term management. Dry storage uses the gas or air as coolant with passive cooling and neutron shielding materials was used instead of water in wet storage system. It is relatively safe and emits little radioactive waste for the storage. As short term actions for the limited storage capacity of spent fuel pool, it is considered to use dry interim/long term storage method to increase the capacity of spent nuclear fuel storage facilities. For 10-year cooled down spent fuel in the pool storage, fuel rod temperature inside metal cask is expected over 250 .deg. C in simulation. Although it satisfied the criteria that cladding temperature of the spent fuel should keep under 400 .deg. C during storage period, high temperature inside cask can accelerate the thermal degradation of the structural materials consisting metal cask and fuel assembly as well as limitation of the storage capacity of metal cask. In this paper, heatpipe-based cooling device for the dry storage cask was suggested for

When volcanism dominates heat transport, a terrestrial body enters a heat-pipe mode, in which hot magma moves through the lithosphere in narrow channels. Even at high heat flow, a heat-pipe planet develops a thick, cold, downwards-advecting lithosphere dominated by (ultra-)mafic flows and contractional deformation at the surface. Heat-pipes are an important feature of terrestrial planets at high heat flow, as illustrated by Io. Evidence for their operation early in Earth's history suggests that all terrestrial bodies should experience an episode of heat-pipe cooling early in their histories.

This book presents the fundamental fluid flow and heat transfer principles occurring in oscillating heatpipes and also provides updated developments and recent innovations in research and applications of heatpipes. Starting with fundamental presentation of heatpipes, the focus is on oscillating motions and its heat transfer enhancement in a two-phase heat transfer system. The book covers thermodynamic analysis, interfacial phenomenon, thin film evaporation, theoretical models of oscillating motion and heat transfer of single phase and two-phase flows, primary factors affecting oscillating motions and heat transfer, neutron imaging study of oscillating motions in an oscillating heatpipes, and nanofluid’s effect on the heat transfer performance in oscillating heatpipes. The importance of thermally-excited oscillating motion combined with phase change heat transfer to a wide variety of applications is emphasized. This book is an essential resource and learning tool for senior undergraduate, gradua...

An experimental program to evaluate noncondensable gas generation in ammonia heatpipes was completed. A total of 37 heatpipes made of aluminum, stainless steel and combinations of these materials were processed by various techniques, operated at different temperatures and tested at low temperature to quantitatively determine gas generation rates. In order of increasing stability are aluminum/stainless combination, all aluminum and all stainless heatpipes. One interesting result is the identification of intentionally introduced water in the ammonia during a reflux step as a means of surface passivation to reduce gas generation in stainless-steel/aluminum heatpipes.

This is the presentation file for the short course Introduction to HeatPipes, to be conducted at the 2015 Thermal Fluids and Analysis Workshop, August 3-7, 2015, Silver Spring, Maryland. NCTS 21070-15. Course Description: This course will present operating principles of the heatpipe with emphases on the underlying physical processes and requirements of pressure and energy balance. Performance characterizations and design considerations of the heatpipe will be highlighted. Guidelines for thermal engineers in the selection of heatpipes as part of the spacecraft thermal control system, testing methodology, and analytical modeling will also be discussed.

As an arising issue for inherent safety of nuclear power plant, the concept of hybrid heatpipe as passive in-core cooling systems was introduced. Hybrid heatpipe has unique features that it is inserted in core directly to remove decay heat from nuclear fuel without any changes of structures of existing facilities of nuclear power plant, substituting conventional control rod. Hybrid heatpipe consists of metal cladding, working fluid, wick structure, and neutron absorber. Same with working principle of the heatpipe, heat is transported by phase change of working fluid inside metal cask. Figure 1 shows the systematic design of the hybrid heatpipe cooling system. In this study, the concept of a hybrid heatpipe was introduced as a Passive IN-core Cooling Systems (PINCs) and demonstrated for internal design features of heatpipe containing neutron absorber. Using a commercial CFD code, single hybrid heatpipe model was analyzed to evaluate thermal performance in designated operating condition. Also, 1-dimensional reactor transient analysis was done by calculating temperature change of the coolant inside reactor pressure vessel using MATLAB. As a passive decay heat removal device, hybrid heatpipe was suggested with a concept of combination of heatpipe and control rod. Hybrid heatpipe has distinct feature that it can be a unique solution to cool the reactor when depressurization process is impossible so that refueling water cannot be injected into RPV by conventional ECCS. It contains neutron absorber material inside heatpipe, so it can stop the reactor and at the same time, remove decay heat in core. For evaluating the concept of hybrid heatpipe, its thermal performance was analyzed using CFD and one-dimensional transient analysis. From single hybrid heatpipe simulation, the hybrid heatpipe can transport heat from the core inside to outside about 18.20 kW, and total thermal resistance of hybrid heatpipe is 0.015 .deg. C/W. Due to unique features of long heat

Dielectric liquid for transfer of heat provides liquid flow from the condenser section to the evaporator section in conventional heatpipes. Working fluid is guided or pumped by an array of wire electrodes connected to a high-voltage source.

A heatpipe of new design, using an electrode structure to orient and guide the dielectric liquid phase flow, is proposed. Analysis indicates that the operation of the electrohydrodynamic heatpipe is in direct analogy to capillary devices, with the polarization force acting in place of capillarity. Advantages of these new heatpipes include greatly reduced liquid friction, electrohydrodynamically enhanced evaporation and condensation heat transfer, and a possible voltage-controlled on/off feature. Preliminary calculations indicate that relatively high performance devices are possible.

Improved methods of heat dissipation are required for modern, high-power density electronic systems. As increased functionality is progressively compacted into decreasing volumes, this need will be exacerbated. High-performance chip power is predicted to increase monotonically and rapidly with time. Systems utilizing these chips are currently reliant upon decades of old cooling technology. Heatpipes offer a solution to this problem. Heatpipes are passive, self-contained, two-phase heat dissipation devices. Heat conducted into the device through a wick structure converts the working fluid into a vapor, which then releases the heat via condensation after being transported away from the heat source. Heatpipes have high thermal conductivities, are inexpensive, and have been utilized in previous space missions. However, the cylindrical geometry of commercial heatpipes is a poor fit to the planar geometries of microelectronic assemblies, the copper that commercial heatpipes are typically constructed of is a poor CTE (coefficient of thermal expansion) match to the semiconductor die utilized in these assemblies, and the functionality and reliability of heatpipes in general is strongly dependent on the orientation of the assembly with respect to the gravity vector. What is needed is a planar, semiconductor-based heatpipe array that can be used for cooling of generic MCM (multichip module) assemblies that can also function in all orientations. Such a structure would not only have applications in the cooling of space electronics, but would have commercial applications as well (e.g. cooling of microprocessors and high-power laser diodes). This technology is an improvement over existing heatpipe designs due to the finer porosity of the wick, which enhances capillary pumping pressure, resulting in greater effective thermal conductivity and performance in any orientation with respect to the gravity vector. In addition, it is constructed of silicon, and thus is better

An electrohydrodynamic heatpipe of radical design is proposed which substitutes polarization electrohydrodynamic force effects for capillarity in collecting, guiding, and pumping a condensate liquid phase. The discussed device is restricted to the use of dielectric liquids as working fluids. Because of the relatively poor thermal transport properties of these liquids, capillary heatpipes using these liquids have not been high performance devices. The employment of the electrohydrodynamic concept should enhance this performance and help fill the performance gap that exists in the temperature range from 250 F to 750 F for 'conventional' capillary heatpipes.

The trend in commercial electronics packaging to deliver ever smaller component packaging has enabled the development of new highly integrated modules meeting the demands of the next generation nano satellites. At under ten kilograms, these nano satellites will require both a greater density electronics and a melding of satellite structure and function. Better techniques must be developed to remove the subsequent heat generated by the active components required to-meet future computing requirements. Integration of commercially available electronics must be achieved without the increased costs normally associated with current generation multi chip modules. In this paper we present a method of component integration that uses silicon heatpipe technology and advanced flexible laminate circuit board technology to achieve thermal control and satellite structure. The' electronics/heatpipe stack then becomes an integral component of the spacecraft structure. Thermal management on satellites has always been a problem. The shrinking size of electronics and voltage requirements and the accompanying reduction in power dissipation has helped the situation somewhat. Nevertheless, the demands for increased onboard processing power have resulted in an ever increasing power density within the satellite body. With the introduction of nano satellites, small satellites under ten kilograms and under 1000 cubic inches, the area available on which to place hot components for proper heat dissipation has dwindled dramatically. The resulting satellite has become nearly a solid mass of electronics with nowhere to dissipate heat to space. The silicon heatpipe is attached to an aluminum frame using a thermally conductive epoxy or solder preform. The frame serves three purposes. First, the aluminum frame provides a heat conduction path from the edge of the heatpipe to radiators on the surface of the satellite. Secondly, it serves as an attachment point for extended structures attached

The vapor flow in a heatpipe was mathematically modeled and the equations governing the transient behavior of the core were solved numerically. The modeled vapor flow is transient, axisymmetric (or two-dimensional) compressible viscous flow in a closed chamber. The two methods of solution are described. The more promising method failed (a mixed Galerkin finite difference method) whereas a more common finite difference method was successful. Preliminary results are presented showing that multi-dimensional flows need to be treated. A model of the liquid phase of a high temperature heatpipe was developed. The model is intended to be coupled to a vapor phase model for the complete solution of the heatpipe problem. The mathematical equations are formulated consistent with physical processes while allowing a computationally efficient solution. The model simulates time dependent characteristics of concern to the liquid phase including input phase change, output heat fluxes, liquid temperatures, container temperatures, liquid velocities, and liquid pressure. Preliminary results were obtained for two heatpipe startup cases. The heatpipe studied used lithium as the working fluid and an annular wick configuration. Recommendations for implementation based on the results obtained are presented. Experimental studies were initiated using a rectangular heatpipe. Both twin beam laser holography and laser Doppler anemometry were investigated. Preliminary experiments were completed and results are reported.

The heat transport and lithospheric dynamics of early Earth are currently explained by plate tectonic and vertical tectonic models, but these do not offer a global synthesis consistent with the geologic record. Here we use numerical simulations and comparison with the geologic record to explore a heat-pipe model in which volcanism dominates surface heat transport. These simulations indicate that a cold and thick lithosphere developed as a result of frequent volcanic eruptions that advected surface materials downwards. Declining heat sources over time led to an abrupt transition to plate tectonics. Consistent with model predictions, the geologic record shows rapid volcanic resurfacing, contractional deformation, a low geothermal gradient across the bulk of the lithosphere and a rapid decrease in heat-pipe volcanism after initiation of plate tectonics. The heat-pipe Earth model therefore offers a coherent geodynamic framework in which to explore the evolution of our planet before the onset of plate tectonics.

An array of a plurality of heatpipe are mounted in spaced relationship to one another with the hot end of the heatpipes in a heated environment, e.g. the exhaust flue of a furnace, and the cold end outside the furnace. Heat conversion equipment is connected to the cold end of the heatpipes.

Full Text Available This article aims to study the in-plane stiffness estimation of heatpipe supporter (a large lattice structure using experimental and numerical methods. The in-plane stiffness of heatpipe supporter for nuclear power plant is very important because of the safety against natural disasters, such as seismic load or tsunami, and has to be evaluated because it greatly affects the durability of the heat exchanger. However, the modeling process of the whole lattice structure for finite element analysis increases resources needed caused by too many nodes and elements. In this study, the mechanical properties of large lattice structures are determined by a unit cell finite element analysis. The mechanical behavior of a large lattice structure has been estimated by finite element analysis through a homogenization process for reducing analysis time and efforts. The finite element analysis results have been verified and show a good agreement with the experimental results.

Observations of the surfaces of all terrestrial bodies other than Earth reveal remarkable but unexplained similarities: endogenic resurfacing is dominated by plains-forming volcanism with few identifiable centers, magma compositions are highly magnesian (mafic to ultra-mafic), tectonic structures are dominantly contractional, and ancient topographic and gravity anomalies are preserved to the present. Here we show that cooling via volcanic heatpipes may explain these observations and provide a universal model of the way terrestrial bodies transition from a magma-ocean state into subsequent single-plate, stagnant-lid convection or plate tectonic phases. In the heat-pipe cooling mode, magma moves from a high melt-fraction asthenosphere through the lithosphere to erupt and cool at the surface via narrow channels. Despite high surface heat flow, the rapid volcanic resurfacing produces a thick, cold, and strong lithosphere which undergoes contractional strain forced by downward advection of the surface toward smaller radii. We hypothesize that heat-pipe cooling is the last significant endogenic resurfacing process experienced by most terrestrial bodies in the solar system, because subsequent stagnant-lid convection produces only weak tectonic deformation. Terrestrial exoplanets appreciably larger than Earth may remain in heat-pipe mode for much of the lifespan of a Sun-like star.

Solar Fundamentals, Inc.'s hot water system employs space-derived heatpipe technology. It is used by a meat packing plant to heat water for cleaning processing machinery. Unit is complete system with water heater, hot water storage, electrical controls and auxiliary components. Other than fans and a circulating pump, there are no moving parts. System's unique design eliminates problems of balancing, leaking, corroding, and freezing.

Design of primary heat transport (PHT) piping of pressurised heavy water reactors (PHWR) has to ensure implementation of leak-before-break concepts. In order to be able to do so, the ductile fracture characteristics of PHT piping material have to be quantiﬁed. In this paper, the fracture resistance of SA333, Grade 6 steel — the material used for Indian PHWR — under monotonic and cyclic tearing loading has been documented. An attempt has also been made to understand the mechanism responsible for the high fracture toughness of the steel through determination of the effect of constraint on the fracture behaviour and fractographic observations. From J–R tests over a range of temperatures, it was observed that SA333 steel exhibits embrittlement tendencies in the service temperature regime. The fracture resistance of the steel is inferior in the longitudinal direction with respect to the pipe geometry as compared to that in the circumferential direction. Imposition of cyclic unloading during ductile fracture tests for simulation of response to seismic activities results in a dramatic decrease of fracture resistance. It appears, from the observations of effects of constraint on fracture toughness and fractographic examinations, that fracture resistance of the steel is derived partly from the inability of voids to initiate and grow due to a loss of constraint in the crack-tip stress ﬁeld.

In many plants, including nuclear power plants, pipelines are composed of numerous fittings such as elbows. When plants use these fittings, welding points need to be increased, and the number of inspections also then increases. As an alternative to welding, the pipe bending process forms bent pipe by applying strain at low or high temperatures. This work investigates how heat treatment affects on the boric acid corrosion of ASME SA335 Gr. P22 caused by the induction heat bending process. Microstructure analysis and immersion corrosion tests were performed. It was shown that every area of the induction heat bent pipe exhibited a high corrosion rate in the boric acid corrosion test. This behavior was due to the enrichment of phosphorous in the ferrite phase, which occurred during the induction heat bending process. This caused the ferrite phase to act as a corrosion initiation site. However, when re-heat treatment was applied after the bending process, it enhanced corrosion resistance. It was proved that this resistance was closely related to the degree of the phosphorus segregation in the ferrite phase.

Metal-foil reed valve in conventional slab-wick heatpipe limits heat flow to one direction only. With sink warmer than source, reed is forced closed and fluid returns to source side through annular transfer wick. When this occurs, wick slab on sink side of valve dries out and heatpipe ceases to conduct heat.

In this article the heat performance of the heatpipe thermosiphon is achieved through numerical model. The heat performance is calculated from few simplified equations which depends on the working fluid and geometry. Also the thermal conductivity is good to mentioning, because is really interesting how big differences are between heatpipes and full solid surfaces.

The role of entrainment in limiting heatpipe power handling capacity is discussed. The effect of entrainment on the measured temperature field in the integral heatpipe of a split system solar cooker is analyzed. An experimental set-up depicting a heat loop is presented, along with test results.

The applicability of using heatpipe principles to cool gas turbine vanes is addressed in this beginning program. This innovative concept involves fitting out the vane interior as a heatpipe and extending the vane into an adjacent heat sink, thus transferring the vane incident heat transfer through the heatpipe to heat sink. This design provides an extremely high heat transfer rate and an uniform temperature along the vane due to the internal change of phase of the heatpipe working fluid. Furthermore, this technology can also eliminate hot spots at the vane leading and trailing edges and increase the vane life by preventing thermal fatigue cracking. There is also the possibility of requiring no bleed air from the compressor, and therefore eliminating engine performance losses resulting from the diversion of compressor discharge air. Significant improvement in gas turbine performance can be achieved by using heatpipe technology in place of conventional air cooled vanes. A detailed numerical analysis of a heatpipe vane will be made and an experimental model will be designed in the first year of this new program.

A loop heatpipe must start successfully before it can commence its service. The startup transient represents one of the most complex phenomena in the loop heatpipe operation. This paper discusses various aspects of loop heatpipe startup behaviors. Topics include the four startup scenarios, the initial fluid distribution between the evaporator and reservoir that determines the startup scenario, factors that affect the fluid distribution between the evaporator and reservoir, difficulties encountered during the low power startup, and methods to enhance the startup success. Also addressed are the pressure spike and pressure surge during the startup transient, and repeated cycles of loop startup and shutdown under certain conditions.

A nitrogen heatpipe was designed, built and tested for the purpose of providing a thermal shunt between the two stages of a Gifford-McMahan (GM) cryocooler during cooldown. The nitrogen heatpipe has an operating temperature range between 63 and 123 K. While the heatpipe is in the temperature range during the system cooldown, it acts as a thermal shunt between the first and second stage of the cryocooler. The heatpipe increases the heat transfer to the first stage of the cryocooler, thereby reducing the cooldown time of the system. When the heatpipe temperature drops below the triple point, the nitrogen working fluid freezes, effectively stopping the heatpipe operation. A small heat leak between cryocooler stages remains because of axial conduction along the heatpipe wall. As long as the heatpipe remains below 63 K, the heatpipe remains inactive. Heatpipe performance limits were measured and the optimum fluid charge was determined.

A family of heatpipe reactors design concepts has been developed to provide heat to a variety of electrical conversion systems. Three power plants are described that span the power range 1-500 kWe and operate in the temperature range 1200-1700 K. The reactors are fast, compact, heat-pipe cooled, high-temperature nuclear reactors fueled with fully enriched refractory fuels, UC-ZrC or UO2. Each fuel element is cooled by an axially located molybdenum heatpipe containing either sodium or lithium vapor. Virtues of the reactor designs are the avoidance of single-point failure mechanisms, the relatively high operating temperature, and the expected long lifetimes of the fuel element components.

A thermal pipe is described which contains a hermetically sealed body with a reticular filler. In order to increase the transmitted thermal power, the pipe is equipped with a high voltage source and with insulators, located between the wall of the body and the filler, where the latter is switched in to the high voltage source, preferably an adjustable one.

Full Text Available The aim of this study was to perform life testing and determine the effect of working fluid on the corrosion of a heatpipe with a sintered wick. The heatpipe was made from a copper tube. The inner heatpipe was filled with 99.97% pure copper powder as a dendritic for the sintering process. The heatpipe had an outer diameter of 6 mm with a length of 200 mm, and distilled water and ethanol were the working fluids. The operating temperature at the evaporator was 125°C. The analysis consisted of using a scanning electron microscope, energy dispersive X-ray spectrometry and atomic absorption spectroscopy. The results of the scanning electron microscope and energy dispersive X-ray spectrometry analysis showed that the corrosion of the heatpipe was uniform. The result of the atomic absorption spectroscopy indicated that the concentration of the copper in the ethanol as the working fluid was greater than in the distilled water as the working fluid, and the highest concentration of copper particles in the ethanol was 22.7499 ppm or 0.0409 mg after testing for 3000 h. The concentration of copper was higher when the length of the life test increased due to corrosion of the heatpipe.

The main concern with the Fukushima accident was the failure of active and passive core cooling systems. The main function of existing passive decay heat removal systems is feeding additional coolant to the reactor core. Thus, an established emergency core cooling system (ECCS) cannot operate properly because of impossible depressurization under the station blackout (SBO) condition. Therefore, a new concept for passive decay heat removal system is required. In this study, an innovative hybrid control rod concept is considered for passive in-core decay heat removal that differs from the existing direct vessel injection core cooling system and passive auxiliary feedwater system (PAFS). The heat transfer between the evaporator and condenser sections occurs by phase change of the working fluid and capillary action induced by wick structures installed on the inner wall of the heatpipe. In this study, a hybrid control rod is developed to take the roles of both neutron absorption and heat removal by combining the functions of a heatpipe and control rod. Previous studies on enhancing the heat removal capacity of heatpipes used nanofluids, self-rewetting fluids, various wick structures and condensers. Many studies have examined the thermal performances of heatpipes using various nanofluids. They concluded that the enhanced thermal performance of the heatpipe using nanofluids is due to nanoparticle deposition on the wick structures. Thus, the wick structure of heatpipes has been modified by nanoparticle deposition to enhance the heat removal capacity. However, previous studies used relatively small heatpipes and narrow ranges of heat loads. The environment of a nuclear reactor is very specific, and the decay heat produced by fission products after shutdown is relatively large. Thus, this study tested a large-scale heatpipe over a wide range of power. The concept of a hybrid heatpipe for an advanced in-core decay heat removal system was introduced for complete

Thermal management is critical to space exploration efforts. In particular, efficient transfer and control of heat flow is essential when operating high energy sources such as nuclear reactors. Thermal energy must be transferred to various energy conversion devices, and to radiators for safe and efficient rejection of excess thermal energy. Applications for space power demand exceptionally long periods of time with equipment that is accessible for limited maintenance only. Equally critical is the hostile and alien environment which includes high radiation from the reactor and from space (galactic) radiation. In space or lunar applications high vacuum is an issue, while in Martian operations the systems will encounter a CO2 atmosphere. The effect of contact at high temperature with local soil (regolith) in surface operations on the moon or other terrestrial bodies (Mars, asteroids) must be considered.

This article discusses about device, which is called heatpipe. This device is with heat source with radiant heat source. Heatpipe is device with high efficiency of heat transfer. The heatpipe, which is describe in this article is termosyphon heatpipe. The experiment with termosyphon heatpipe get a result. On the base of result, it will be in future to create mathematical model in Ansys. Thermosyphon heatpipe is made of copper and distilled water is working fluid. The significance of this experiment consists in getting of the heat transfer and performance characteristic. On the basis of measured and calculated data can be constructed the plots.

An expanded heatpipe operating model is described which includes thermodynamic and heat transfer considerations to reconcile disparities between actual and theoretical heatpipe performances. The analysis shows that thermodynamic considerations can explain the observed heatpipe performance limitations. A full understanding of thermodynamic processes could lead to advanced concepts for thermal transport devices.

This paper details the design, construction and partial analysis of a low temperature flat heatpipe in order to determine the feasibility of implementing flat heatpipes into thermophotovoltaic (TPV) energy conversion systems.

Heatpipes are two-phase heat transfer devices with extremely high effective thermal conductivity. They can be cylindrical or planar in structure. Heatpipes can be embedded in a metal cooling plate, which is attached to the heat source, and can also be assembled with a fin stack for fluid heat transfer. Due to the high heat transport capacity, heat exchangers with heatpipes have become much smaller than traditional heat exchangers in handling high heat fluxes. With the working fluid in a heatpipe, heat can be absorbed on the evaporator region and transported to the condenser region where the vapour condenses releasing the heat to the cooling media. Heatpipe technology has found increasing applications in enhancing the thermal performance of heat exchangers in microelectronics, energy and other industrial sectors. Utilisation of a heatpipe fin stack in the drying cycle of domestic appliances for heat recovery may lead to a significant energy saving in the domestic sector. However, the design of the heatpipeheat exchanger will meet a number of challenges. This paper presents a design method by using CFD simulation of the dehumidification process with heatpipeheat exchangers. The strategies of simulating the process with heatpipes are presented. The calculated results show that the method can be further used to optimise the design of the heatpipe fin stack. The study suggests that CFD modelling is able to predict thermal performance of the dehumidification solution with heatpipeheat exchangers. (Author)

Mochizuki et al. was suggested the passive cooling system to spent nuclear fuel pool. Detail analysis of various heatpipe design cases was studied to determine the heatpipes cooling performance. Wang et al. suggested the concept PRHRS of MSR using sodium heatpipes, and the transient performance of high temperature sodium heatpipe was numerically simulated in the case of MSR accident. The meltdown at the Fukushima Daiichi nuclear power plants alarmed to the dangers of station blackout (SBO) accident. After the SBO accident, passive decay heat removal systems have been investigated to prevent the severe accidents. Mochizuki et al. suggested the heatpipes cooling system using loop heatpipes for decay heat removal cooling and analysis of heatpipe thermal resistance for boiling water reactor (BWR). The decay heat removal systems for pressurized water reactor (PWR) were suggested using natural convection mechanisms and modification of PWR design. Our group suggested the concept of a hybrid heatpipe with control rod as Passive IN-core Cooling System (PINCs) for decay heat removal for advanced nuclear power plant. Hybrid heatpipe is the combination of the heatpipe and control rod. In the present research, the main objective is to investigate the effect of the inner structure to the heat transfer performance of heatpipe containing neutron absorber material, B{sub 4}C. The main objective is to investigate the effect of the inner structure in heatpipe to the heat transfer performance with annular flow path. ABS pellet was used instead of B{sub 4}C pellet as cylindrical structures. The thermal performances of each heatpipes were measured experimentally. Among them, concentric heatpipe showed the best performance compared with others. 1. Annular evaporation section heatpipe and annular flow path heatpipe showed heat transfer degradation. 2. AHP also had annular vapor space and contact cooling surface per unit volume of vapor was increased. Heat transfer

After Fukushima accident, importance and necessity of passive safety for nuclear power plant have been emphasized. Due to its passive characteristic, heatpipe is seriously considered as an alternative device of the active safety system for removing decay heat from the reactor core. Among many possible applications of heatpipe in NPP, we considered the application to the control rod. In the situation of SBO(Station Black Out) due to BDBA(Beyond Design Basis Accident) in a PWR, control rods are dropped in to nuclear reactor core automatically. Thus, it is expected that applying heatpipe function to control rod can enhance reactor safety by removing decay heat of fuel assembly. Considering the height of the control rod, L/D of the heatpipe would be larger than 400 if the given diameter is assumed to be similar to the diameter of the control rod. Thus, it may not be the matter for small heatpipes, it is necessary to consider the effects of L/D for the large L/D heatpipes. There for, length effect on the thermal performance of heatpipe for decay heat removal was experimentally investigated in this study. Through this study, the L/D effect on the thermal performance of the large L/D heatpipe for nuclear reactor has been studied.

Loop HeatPipes (LHPs) can transport very large thermal power loads, over long distances, through flexible, small diameter tubes and against high gravitational heads. While recent LHPs have transported as much as 1500 W, the peak heat flux through a LHP's evaporator has been limited to about 0.07 MW/m2. This limitation is due to the arrangement of vapor passages next to the heat load which is one of the conditions necessary to ensure self priming of the device. This paper describes work aimed at raising this limit by threefold to tenfold. Two approaches were pursued. One optimized the vapor passage geometry for the high heat flux conditions. The geometry improved the heat flow into the wick and working fluid. This approach also employed a finer pored wick to support higher vapor flow losses. The second approach used a bidisperse wick material within the circumferential vapor passages. The bidisperse material increased the thermal conductivity and the evaporative surface area in the region of highest heat flux, while providing a flow path for the vapor. Proof-of-concept devices were fabricated and tested for each approach. Both devices operated as designed and both demonstrated operation at a heat flux of 0.70 MW/m2. This performance exceeded the known state of the art by a factor of more than six for both conventional heatpipes and for loop heatpipes using ammonia. In addition, the bidisperse-wick device demonstrated boiling heat transfer coefficients up to 100,000 W/m2.K, and the fine pored device demonstrated an orientation independence with its performance essentially unaffected by whether its evaporator was positioned above, below or level with the condenser.

Magnesium has shown promise as a lighter-weight alternative to the aluminum alloys now used to make the main structural components of axially grooved heatpipes that contain ammonia as the working fluid. Magnesium heat-pipe structures can be fabricated by conventional processes that include extrusion, machining, welding, and bending. The thermal performances of magnesium heatpipes are the same as those of equal-sized aluminum heatpipes. However, by virtue of the lower mass density of magnesium, the magnesium heatpipes weigh 35 percent less. Conceived for use aboard spacecraft, magnesium heatpipes could also be attractive as heat-transfer devices in terrestrial applications in which minimization of weight is sought: examples include radio-communication equipment and laptop computers.

This invention is directed to transferring heat from an extremely high temperature source to an electrically isolated lower temperature receiver. The invention is particularly concerned with supplying thermal power to a thermionic converter from a nuclear reactor with electric isolation. Heat from a high temperature heatpipe is transferred through a vacuum or a gap filled with electrically nonconducting gas to a cooler heatpipe. If the receiver requires gratr thermal power density, geometries are used with larger heatpipe areas for transmitting and receiving energy than the area for conducting the heat to the thermionic converter. In this way the heatpipe capability for increasing thermal power densities compensates for the comparative low thermal power densities through the electrically nonconducting gap between the two heatpipes.

Heatpipe devices, for their typical working mode, are particularly suitable for zero gravity applications, and have also been considered for applications in space satellites with nuclear generators because of the absence of active systems for the coolant circulation. The present work reports the results of experimental tests carried out on a heatpipe facility designed to investigate the thermal-hydraulic performance of a water heatpipe. The device layout, configuration and geometry, simulate a heatpipe working mode utilizable in space applications under zero gravity conditions. The evaporating section, completely lined (covered) with wicks (sintered stainless steel), and nearly plane shaped, is housed in a cylindrical container. The obtained results show that the system can approach steady-state conditions, at a pressure of 4 bar and with a heat flux transferred of about 150 W/cm2, supporting an electric power step of about 1.8 Kw.

National Aeronautics and Space Administration — This Small Business Innovation Research Phase I project will develop heatpipe and loop heatpipe (LHP) working fluids for what is known as the intermediate...

A heatpipe has an evaporator portion, a condenser portion, and at least one flexible portion that is sealingly coupled between the evaporator portion and the condenser portion. The flexible portion has a flexible tube and a flexible separator plate held in place within the flexible tube so as to divide the flexible tube into a gas-phase passage and a liquid-phase artery. The separator plate and flexible tube are configured such that the flexible portion is flexible in a plane that is perpendicular to the separator plate.

Theory, design, fabrication, testing, and operation of heatpipes are presented in these Federally sponsored research reports. Applications are described in the areas of heating and air conditioning, power generation, electronics cooling, spacecraft, nuclear reactors, cooling engines, and thermodynamics. This updated bibliography contains 70 abstracts, all of which are new entries to the previous edition.

In this research, an innovative hybrid heatpipe system is designed for advanced in-core decay heat removal concept. Heatpipe is a device that transfer heat from pipe's hotter end to the colder end by phase change and convection of working fluid. The concept of the hybrid heatpipe system is that the control rod can have not only the original function of neutron absorber but also the function of the heat removal. If the function of heatpipe is applied to the control rods, the limited heat removal capacity can be extended because control rods are inserted to the reactor at initial state of accident using gravitational force. The neutron absorber-based heatpipe is designed to apply them to nuclear systems. However, thermosyphon and heatpipe are competitive as passive decay heat removal device in large scale. Thus, stainless steel 316L thermosyphon and heatpipe having sheath outer diameter of 3/4 inch (17.4 mm inner diameter), and the length of 1000 mm were tested. Effects on whether there is a wick structure on the heatpipe or not on the heat removal capacity were studied. To confirm the heat removal capacity of heatpipe, and heat transfer coefficient were measured for each specimen.

Recently, passive safety systems are under development to ensure the core cooling in accidents involving impossible depressurization such as station blackout (SBO). Hydraulic control rod drive mechanisms, passive auxiliary feedwater system (PAFS), Passive autocatalystic recombiner (PAR), and so on are types of passive safety systems to enhance the safety of nuclear power plants. Heatpipe is used in various engineering fields due to its advantages in terms of easy fabrication, high heat transfer rate, and passive heat transfer. Also, the various concepts associated with safety system and heat transfer using the heatpipe were developed in nuclear engineering field.. Thus, our group suggested the hybrid control rod which combines the functions of existing control rod and heatpipe. If there is significant temperature difference between active core and condenser, the hybrid control rod can shutdown the nuclear fission reaction and remove the decay heat from the core to ultimate heat sink. The unique characteristic of the hybrid control rod is the presence of neutron absorber inside the heatpipe. Many previous researchers studied the effect of parameters on the thermal performance of heatpipe. However, the effect of neutron absorber on the thermal performance of heatpipe has not been investigated. Thus, the annular heatpipe which contains B{sub 4}C pellet in the normal heatpipe was prepared and the thermal performance of the annular heatpipe was studied in this study. Hybrid control rod concept was developed as a passive safety system of nuclear power plant to ensure the safety of the reactor at accident condition. The hybrid control rod must contain the neutron absorber for the function as a control rod. So, the effect of neutron absorber on the thermal performance of heatpipe was experimentally investigated in this study. Temperature distributions at evaporator section of annular heatpipe were lower than normal heatpipe due to the larger volume occupied by

HeatPipes, 6th Edition, takes a highly practical approach to the design and selection of heatpipes, making it an essential guide for practicing engineers and an ideal text for postgraduate students. This new edition has been revised to include new information on the underlying theory of heatpipes and heat transfer, and features fully updated applications, new data sections, and updated chapters on design and electronics cooling. The book is a useful reference for those with experience and an accessible introduction for those approaching the topic for the first time. Contains all informat

In precision machining, the machining error from thermal distortion carries a high proportion of the total errors. If a precision machining tool can transfer heat fast, the thermal distortion will be reduced and the machining precision will be improved. A heatpipe working based on phase transitions of the inner working liquid transfers heat with high efficiency and is widely applied in spaceflight and chemical industries. In mechanics, applications of heatpipes are correspondingly less. When a heatpipe is applied to a hydrostatic motor-ized spindle, the thermal distortion cannot be solved dur-ing the heat transfer process because thermal conductivity or equivalent thermal conductivity should be provided first for special application in mechanics. An equivalent thermal conductivity model based on equivalent thermal resistances is established. Performance tests for a screen wick pipe, gravity pipe, and rotation heatpipe are done to validate the efficiency of the equivalent thermal conduc-tivity model. The proposed model provides a calculation method for the thermal distortion analysis of heatpipes applied in the motorized spindle.

A multileg heatpipe evaporator facilitates the use and application of a monogroove heatpipe by providing an evaporation section which is compact in area and structurally more compatible with certain heat exchangers or heat input apparatus. The evaporation section of a monogroove heatpipe is formed by a series of parallel legs having a liquid and a vapor channel and a communicating capillary slot therebetween. The liquid and vapor channels and interconnecting capillary slots of the evaporating section are connected to the condensing section of the heatpipe by a manifold connecting liquid and vapor channels of the parallel evaporation section legs with the corresponding liquid and vapor channels of the condensing section.

This paper discusses the concept of an arterial heatpipe with a capillary driven jet pump. The jet pump generates a suction which pumps vapor and noncondensible gas from the artery. The suction also forces liquid into the artery and maintains it in a primed condition. A theoretical model was developed which predicts the existence of two stable ranges. Up to a certain tilt the artery will prime by itself once a heat load is applied to the heatpipe. At higher tilts, the jet pump can maintain the artery in a primed condition but self-priming is not possible. A prototype heatpipe was tested which self-primed up to a tilt of 1.9 cm, with a heat load of 500 watts. The heatpipe continued to prime reliably when operated as a VCHP, i.e., after a large amount of noncondensible gas was introduced.

A multileg heatpipe evaporator facilitates the use and application of a monogroove heatpipe by providing an evaporation section which is compact in area and structurally more compatible with certain heat exchangers or heat input apparatus. The evaporation section of a monogroove heatpipe is formed by a series of parallel legs having a liquid and a vapor channel and a communicating capillary slot therebetween. The liquid and vapor channels and interconnecting capillary slots of the evaporating section are connected to the condensing section of the heatpipe by a manifold connecting liquid and vapor channels of the parallel evaporation section legs with the corresponding liquid and vapor channels of the condensing section.

A 15,000 watt spacecraft waste heat rejection system utilizing heatpipe radiator panels was investigated. Of the several concepts initially identified, a series system was selected for more in-depth analysis. As a demonstration of system feasibility, a nominal 500 watt radiator panel was designed, built and tested. The panel, which is a module of the 15,000 watt system, consists of a variable conductance heatpipe (VCHP) header, and six isothermalizer heatpipes attached to a radiating fin. The thermal load to the VCHP is supplied by a Freon-21 liquid loop via an integral heat exchanger. Descriptions of the results of the system studies and details of the radiator design are included along with the test results for both the heatpipe components and the assembled radiator panel. These results support the feasibility of using heatpipes in a spacecraft waste heat rejection system.

Separate type heatpipeheat exchangers are often used for large-scale heat exchanging. The arrangement of such a heat exchanger conveniently allows heat input to and output from the heat exchanger at remote locations. The traditional method of designing an ordinary HPHE (heatpipeheat exchanger) is commonly applied in the separate type exchanger design, but the calculations have to be carried out separately, which makes it very complicated. In this work, the ε-NTU (effectiveness-Number of Transfer Units) method was applied for optimization analysis of single- or multi-level separate type heatpipeheat exchangers. An optimizing formula for single-level separate type heatpipeheat exchangers was obtained. The optimizing principles of effectiveness-NTU and heat transfer rate by the equal distribution method for multi-level separate type heatpipeheat exchanger are presented. The design of separate type heatpipeheat exchangers by the optimizing method is more convenient and faster than by the traditional method.

A test plan is given which describes the tests to be conducted on several typical solar receiver heatpipes. The hardware to be used, test fixtures and rationale of the test program are discussed. The program objective is to perform life testing under simulated receiver conditions, and to conduct performance tests with selected heatpipes to further map their performance, particularly with regard to their transient behavior. Performance requirements are defined. Test fixtures designed for the program are described in detail, and their capabilities for simulating the receiver conditions and their limitations are discussed. The heatpipe design is given. (LEW)

The effect of noncondensable gases on high performance arterial heatpipes has been investigated both analytically and experimentally. Models have been generated which characterize the dissolution of gases in condensate and the diffusional loss of dissolved gases from condensate in arterial flow. These processes, and others, have been used to postulate stability criteria for arterial heatpipes. Experimental observations of gas occlusions were made using a stainless steel heatpipe equipped with viewing ports, and the working fluids methanol and ammonia with the gas additives helium, argon, and xenon. Observations were related to gas transport models.

The use of large surfaced aluminum roll bond panels with an integral flow system as heatpipes is studied. With a suitable flow system e.g., parallel passages with a cross-connection, one single filling procedure is required for the operating medium. Adequate materials for the manufacture of heatpipes are Al 99,3; AlMn1, 5 and AlMn1, 5Sil,5. Peel, creep and burst tests as well as corrosion tests were made on specimens and structural elements of these materials. Results show that the use of such panels for heatpipe manufacturing is appropriate for limited maximum temperature applications. Prototypes of heatpipes and their characteristic features are described in view of their use as absorbers in solar collectors. Good heat exchange performances obtained.

Full Text Available Work is devoted to a research of spined heat-exchanging pipes that are assumed to use in air-cooler exchangers (ACE. The proposed new geometry of finning allows intensifying heat exchange and improving the efficiency of air coolers. It is caused by the increased area of finned surface with a value of finning ratio (the ratio of the area of the smooth pipe to a finned one to 42.7, while in the commercially available ACE, the figure is 22. Besides, the geometrical arrangement of the pin fins turbulizes the airflow. It should be mentioned that an easier method of manufacturing of heat exchanging pipes is proposed to use, which will reduce their costs. The proposed heat exchange pipes are made by winding cut aluminum strip to the supporting pipe or stretching stamped blanks on it. To increase the efficiency of the heat exchange surface pin fins should be as thin and long as possible; however, their strength should be sufficient for deformation-free operation. Fins should be staggered to maximize the distance between them. Spined heat-exchange pipes are designed to operate in a commercially produced ACE and their service is carried out similarly to commercially produced transversely finned pipes.

National Aeronautics and Space Administration — The objective of the Phase II program is to complete the development of the titanium heatpipe thermal plane and establish all necessary steps for production of this...

National Aeronautics and Space Administration — Wick properties are often the limiting factor in a heatpipe design. Current technology uses conventional sintering of metal powders, screen wick, or grooves to...

The meeting was concerned with the use of low grade nuclearheat for district heating, desalination, process heat, and agriculture and aquaculture. The sessions covered applications and demand, heat sources, and economics.

Heatpipe is device working with phase changes of working fluid inside hermetically closed pipe at specific pressure. The phase changes of working fluid from fluid to vapor and vice versa help heatpipe to transport high heat flux. The article deal about construction and processes casing in heatpipe during operation. Experiment visualization of working fluid flow is performed with glass heatpipe filed with ethanol. The visualization of working fluid flow explains the phenomena as working fl...

An important niche for nuclear energy is the need for power at remote locations removed from a reliable electrical grid. Nuclear energy has potential applications at strategic defense locations, theaters of battle, remote communities, and emergency locations. With proper safeguards, a 1 to 10-MWe (megawatt electric) mobile reactor system could provide robust, self-contained, and long-term power in any environment. Heatpipe-cooled fast-spectrum nuclear reactors have been identified as a candidate for these applications. Heatpipe reactors, using alkali metal heatpipes, are perfectly suited for mobile applications because their nature is inherently simpler, smaller, and more reliable than “traditional” reactors. The goal of this project was to develop a scalable conceptual design for a compact reactor and to identify scaling issues for compact heatpipe cooled reactors in general. Toward this goal two detailed concepts were developed, the first concept with more conventional materials and a power of about 2 MWe and a the second concept with less conventional materials and a power level of about 5 MWe. A series of more qualitative advanced designs were developed (with less detail) that show power levels can be pushed to approximately 30 MWe.

National Aeronautics and Space Administration — Heatpipes are commonly used for transporting heat over relatively long distances with very low temperature drop. One of the limitations of heatpipes is the...

Hydrogen and chemical heatpipes were proposed as methods of transporting energy from a primary energy source (nuclear, solar) to the user. In the chemical heatpipe system, primary energy is transformed into the energy of a reversible chemical reaction; the chemical species are then transmitted or stored until the energy is required. Analysis of thermochemical hydrogen schemes and chemical heatpipe systems on a second law efficiency or available work basis show that hydrogen is superior especially if the end use of the chemical heatpipe is electrical power.

Hydrogen and chemical heatpipes were proposed as methods of transporting energy from a primary energy source (nuclear, solar) to the user. In the chemical heatpipe system, primary energy is transformed into the energy of a reversible chemical reaction; the chemical species are then transmitted or stored until the energy is required. Analysis of thermochemical hydrogen schemes and chemical heatpipe systems on a second law efficiency or available work basis show that hydrogen is superior especially if the end use of the chemical heatpipe is electrical power.

Recently, there has been put into practical use of heatpipes as space application, electronics cooling, and waste heat recovery. Especially, the low temperature heatpipe which can be used in below atmospheric temperature are also actively developed and applied in terrestrial field. These are based on utilization of natural energy in cold region. This paper is described about application of snow melting and deicing system on a road and roof, snow damage prevention system for electric pole branch wire, artificial permafrost storage system as a reverse utilization of cold atmosphere, and cryo-anchor applied in Alaska and northern Canada.

A heatpipe cooled reactor is one of several candidate reactor cores being considered for advanced space power and propulsion systems to support future space exploration applications. Long life heatpipe modules, with designs verified through a combination of theoretical analysis and experimental lifetime evaluations, would be necessary to establish the viability of any of these candidates, including the heatpipe reactor option. A hardware-based program was initiated to establish the infrastructure necessary to build heatpipe modules. This effort, initiated by Los Alamos National Laboratory and referred to as the Safe Affordable Fission Engine (SAFE) project, set out to fabricate and perform non-nuclear testing on a modular heatpipe reactor prototype that can provide 100 kilowatt from the core to an energy conversion system at 700 C. Prototypic heatpipe hardware was designed, fabricated, filled, closed-out and acceptance tested.

pipes. [0013] Most transducer packages involve a stack of active ceramic. A Tonpilz transducer 10 in the prior art, as depicted in FIG. 1...identical or corresponding parts throughout the several views and wherein: [0023] FIG. 1 is a prior art depiction of a Tonpilz transducer design...Distribution is unlimited 20090916027 Attorney Docket No. 97001 COOLING ACOUSTIC TRANSDUCER WITH HEATPIPES STATEMENT OF GOVERNMENT INTEREST [0001

Experimental research was conducted to understand heat transfer characteristic of pulsating heatpipe in this paper,and the PHP is made of high quality glass capillary tube. Under different fill ratio, heat transfer rate and many other influence factors, the flow patterns were observed in the start-up, transition and stable stage. The effects of heating position on heat transfer were discussed. The experimental results indicate that no annular flow appears in top heating condition. Under different fill ratios and heat transfer rate, the flow pattern in PHP is transferred from bulk flow to semi-annular flow and annular flow, and the performance of heat transfer is improved for down heating case. The experimental results indicate that the total heat resistant of PHP is increased with fill ratio, and heat transfer rate achieves optimum at filling rate 50%. But for pulsating heatpipe with changing diameters the thermal resistance is higher than that with uniform diameters.

Prototype testing of heatpipes for spacecraft heat control was done on board the Interkosmos-15 satellite launched on 19 June 1976. The purpose was to gather data for optimizing the design, namely the capillary structure and the selection of heat transfer agent, as well as to verify the soundness of manufacturing technologies and test procedures. Three heatpipes were tested, each 412 mm long with a 14 mm outside diameter. All had been made of an aluminum alloy. In two pipes the capillary structure consisted of 0.6 x 0.5 mm/sup 2/ rectangular channels running axially along the inside wall, in the third pipe a 1 mm thick tubular mesh of Kh18N10T steel wire running coaxially inside served as the capillary structure. The heat transfer agent was Freon-11 in one of the first two pipes and synthetic liquid ammonia in the other two pipes. The three pipes were mounted radially around a radiator as the hub, with the test conditions controllable by means of an electric heater coil along the evaporation zone of each pipe, resistance thermometers for the evaporation zone and for the condensation zone of each, and also an external cooling fan. The radial distribution of temperature drops along the pipes was measured and the thermal fluxes were calculated, these data being indicative of the performance under conditions of weightlessness over the 0 to 70/sup 0/C temperature range. The somewhat worse performance of the heatpipe with a tubular capillary mesh inside is attributable to formation of vapor bubbles which impede the mass transfer along such an artery.

This paper introduces 'Hybrid control rod' combining its original function and heat removal ability. The high temperature operation and high resistance of radiation should be considered to adopt the hybrid heatpipe at the in-core condition. Other design consideration is to make extra inlet parts because it has a high risk of inlet boundary failure. It means that the introduction of heatpipe system is difficult to present nuclear power plants. The other concepts are presented to out-core cooling design but it has low performance compared with in-core heat removal system. Hybrid heatpipe for in-core heat removal system suggests the solution of these problems. Ultimate objective of this research is to develop the passive emergency decay heat removal system using hybrid heatpipes targeting design bases accidents such as station black-out (SBO) and small break loss of coolant accident (SBLOCA). The purpose of this work is to confirm the performance and heat transfer behavior of hybrid heatpipe. The hybrid heatpipe has special condition for operation. Therefore, it is hard to analyze their behavior in core. Table I shows the characteristics of hybrid heatpipe and consideration for manufacturing the heatpipe.

Full Text Available Heatpipe is device working with phase changes of working fluid inside hermetically closed pipe at specific pressure. The phase changes of working fluid from fluid to vapor and vice versa help heatpipe to transport high heat flux. The article deal about construction and processes casing in heatpipe during operation. Experiment visualization of working fluid flow is performed with glass heatpipe filed with ethanol. The visualization of working fluid flow explains the phenomena as working fluid boiling, nucleation of bubbles, vapor flow, vapor condensation on the wall, vapor and condensate flow interaction, flow down condensate film thickness on the wall, occurred during the heatpipe operation.

Heatpipe is device working with phase changes of working fluid inside hermetically closed pipe at specific pressure. The phase changes of working fluid from fluid to vapor and vice versa help heatpipe to transport high heat flux. The article deal about construction and processes casing in heatpipe during operation. Experiment visualization of working fluid flow is performed with glass heatpipe filed with ethanol. The visualization of working fluid flow explains the phenomena as working fluid boiling, nucleation of bubbles, vapor flow, vapor condensation on the wall, vapor and condensate flow interaction, flow down condensate film thickness on the wall, occurred during the heatpipe operation.

Previous studies have shown that polyurethane insulation (PUR foam) on district heatingpipes acts as protection against water if it is of good quality, i.e. free from cracks, cavities and other defects. On the other hand water vapour easily diffuses through PUR foam. However this is not a problem as long as the steel pipe is warmer than the surface layer, since the high temperature will prevent the vapour from condensating. What will happen with the insulation of a casing free district heatingpipe where the ground water level occasionally reaches above the pipe has not been studied in detail. The current project has studied to what extent moisture enters the PUR foam insulation of two approximately one meter long district heatingpipes without casing which have been in the ground for four years. Occasionally, the ground-water has entirely covered the pipes. In addition, the foam has been studied with respect to damage from the surrounding backfill material. Test specimens were taken out of the casing free pipes and were analysed with respect to moisture content. Additional measurements were done with a moisture indicator, and the electric resistance between the steel pipes and the four surveillance wires in each pipe was measured. The results from the various measurement techniques were the compared. The results show that the PUR foam remains dry as long as the service pipe is hot if no defects, such as crack and cavities, are present. Close to the service pipe, the foam actually dries out over time. The moisture content of the middle layer remains more or less constant. Only the colder parts on the outside exhibit an increase in moisture content. It was also seen that defects may lead to water ingress with subsequent humidification of the foam. However, the damaged foam area is limited. This is not the case for a regular pipe with a vapour tight casing, where experience show that moisture tend to spread along the pipe. The pipes were buried in sand and no

Full Text Available This paper deals with development and studies of a trapezoidal axial grooved nitrogen heatpipe. A special liquid nitrogen cryostat has been designed and developed for evaluating the performance of heatpipe where the condenser portion is connected to the cold sink externally. Experiments have been performed on the heatpipe as well as on an equivalent diameter copper rod at different heat loads. The steady state performance of the heatpipe is compared with that of copper rod.

A research and development program in variable conductance heatpipe technology is reported. The project involved: (1) theoretical and/or experimental studies in hydrostatics, (2) hydrodynamics, (3) heat transfer into and out of the pipe, (4) fluid selection, and (5) materials compatibility. The development, fabrication, and test of the space hardware resulted in a successful flight of the heatpipe experiment on the OAO-3 satellite. A summary of the program is provided and a guide to the location of publications on the project is included.

Full Text Available The heatpipe is one of the cooling media which is potential to be developed for the passive cooling system for nuclear reactors. To enhance the performance of the heatpipe, nanofluids have been used as the working fluid for the heatpipe. This paper studies the characteristics of nanofluids as the working fluid of heatpipe with screen mesh wick, which was the mixture of nano-sized particles (Al2O3 and TiO2 with water as the base fluid. The nanoparticles have average diameter of 20 nm, made with 1% to 5% volume fraction. The heatpipe thermal performance was tested using heater with different heat load. The experimental result shows the use of 5% Al2O3-water improve the thermal performance by reducing the temperature at evaporator side as much as 23.7% and the use of TiO2-water reduce the temperature at evaporator side as much as 20.2% compared to the use of water. The use of nanofluid also decreases the thermal resistance of heatpipe. As the use of nanofluid improves thermal performance of heatpipe, it has a potential for applications along with heatpipes at nuclear reactors

Station blackout (SBO) accident is the event that all AC power is totally lost from the failure of offsite and onsite power sources. Although electricity was provided from installed batteries for active system after shutdown, they were failed due to flooding after tsunami. The vulnerability of the current operating power plant's cooling ability during extended station blackout events is demonstrated and the importance of passive system becomes emphasized. Numerous researches about passive system have been studied for proper cooling residual heat after Fukushima nuclear power plant accident. Heatpipe is the effective passive heat transfer device that latent heat of vaporization is used to transport heat over long distance with even small temperature difference. Since liquid flows due to capillary force from wick structure and steam flows up due to buoyancy force, power is not necessary. Heatpipe is widely used in removal of local hot spot heat fluxes in CPU and thermal management in space crafts and satellites. Hybrid control rod, which consists of heatpipe with B{sub 4}C for wick structure material can be used for removing residual heat after. It can be applied to both for shutdown and cooling of decay heat in reactor. This concept is independent of external reactor situation like operator's mistake or malfunction of active cooling system. Heatpipe cooling system can be applied to Emergency Core Cooling System, In-Vessel Retention, containment and spent fuel cooling, contributing to decrease Core Damage Frequency.

Based on the characteristics of heat transfer for corrugated pipe,a method of calculating and de-sign on the submersible corrugated pipe sewage heat exchanger was put forward theoretically and experimental-ly.The actual movement parameters of air-conditioning system used in this heat exchanger were measured.The experimental result shows that the quantity of heat transfer of the corrugated pipe sewage heat exchanger can satisfy the building's load with the average coefficient of performance 4.55.At the same time.the quantity ot heat transfer of the corrugated pipe sewage heat exchanger was compared with that of the other nonmetallic sewage heat exchangers(i.e.,the plastic-Al pipe sewage heat exchanger and PP-R pipe sewage heat exchanger)experimentally.It is found out that the effect of heat transfer for submersible corrugated pipe sewage heat ex-changer is superior to those of the plastic-Al pipe and the PP-R pipe.The quantity of heat transfer per mile of corrugated pipe sewage heat exchanger is 5.2 times as much as that of the plastic-Al pipe,and it is 8.1 times as much as that of PP-R pipe.

Full Text Available The contribution is listed possible application of heatpipes in systems for obtaining heat from flue gas of small heat sources. It is also stated in the contribution design an experimental device on which to study the impact of fill (the quantity, type of load at various temperature parameters (temperature heating and cooling thermal power transferred to the heatpipe. Is listed measurement methodology using heatpipes designed experimental facility, measurement results and analysis of the results obtained.

Perforated nonwetting plug of material such as polytetrafluoroethylene is mounted in gas reservoir feed tube, preferably at end which extends into heatpipe condenser section, to prevent liquid from entering gas reservoir of passively controlled heatpipe.

A multifunctional sandwich panel combining efficient structural load support and thermal management characteristics has been designed and experimentally assessed. The concept is based upon a truncated, square honeycomb sandwich structure. In closed cell honeycomb structures, the transport of heat from one face to the other occurs by a combination of conduction through the webs and convection/radiation within the cells. Here, much more effective heat transport is achieved by multifunctionally utilizing the core as a heatpipe sandwich panel. Its interior consists of a 6061 aluminum truncated-square honeycomb core covered with a stochastic open-cell nickel foam wick. An electroless nickel plating barrier layer inhibited the chemical reaction between the deionized water working fluid and the aluminum structure, retarding the generation of non-condensable hydrogen gas. A thermodynamic model was used to guide the design of the heatpipe sandwich panel. We describe the results of a series of experiments that validate the operational principle of the multifunctional heatpipe sandwich panel and characterize its transient response to an intense localized heat source. The systems measured thermal response to a localized heat source agrees well with that predicted by a finite difference method model used to predict the thermal response. (author)

Temperature sensing system detects presence of gas slugs in heatpipes. System designed for operation between zero and 70 degrees C and detects noncondensable pockets of gas that result from decomposition of ammonia cooling fluid. Slugs 1 in. (25mm) in length detected.

The work done by Thermacore, Inc., Lancaster, Pennsylvania, for the Phase 1, 1992 SBIR National Aeronautics and Space Administration Contract, 'Insoluble Coatings for Stirling Engine HeatPipe Condenser Surfaces' is described. The work was performed between January 1992 and July 1992. Stirling heat engines are being developed for electrical power generation use on manned and unmanned earth orbital and planetary missions. Dish Stirling solar systems and nuclear reactor Stirling systems are two of the most promising applications of the Stirling engine electrical power generation technology. The sources of thermal energy used to drive the Stirling engine typically are non-uniform in temperature and heat flux. Liquid metal heatpipe receivers are used as thermal transformers and isothermalizers to deliver the thermal energy at a uniform high temperature to the heat input section of the Stirling engine. The use of a heatpipe receiver greatly enhances system efficiency and potential life span. One issue that is raised during the design phase of heatpipe receivers is the potential solubility corrosion of the Stirling engine heat input section by the liquid metal working fluid. This Phase 1 effort initiated a program to evaluate and demonstrate coatings, applied to nickel based Stirling engine heater head materials, that are practically 'insoluble' in sodium, potassium, and NaK. This program initiated a study of nickel aluminide as a coating and developed and demonstrated a heatpipe test vehicle that can be used to test candidate materials and coatings. Nickel 200 and nickel aluminide coated Nickel 200 were tested for 1000 hours at 800 C at a condensation heat flux of 25 W/sq cm. Subsequent analyses of the samples showed no visible sign of solubility corrosion of either coated or uncoated samples. The analysis technique, photomicrographs at 200X, has a resolution of better than 2.5 microns (.0001 in). The results indicate that the heatpipe environment is not directly

The work done by Thermacore, Inc., Lancaster, Pennsylvania, for the Phase 1, 1992 SBIR National Aeronautics and Space Administration Contract, 'Insoluble Coatings for Stirling Engine HeatPipe Condenser Surfaces' is described. The work was performed between January 1992 and July 1992. Stirling heat engines are being developed for electrical power generation use on manned and unmanned earth orbital and planetary missions. Dish Stirling solar systems and nuclear reactor Stirling systems are two of the most promising applications of the Stirling engine electrical power generation technology. The sources of thermal energy used to drive the Stirling engine typically are non-uniform in temperature and heat flux. Liquid metal heatpipe receivers are used as thermal transformers and isothermalizers to deliver the thermal energy at a uniform high temperature to the heat input section of the Stirling engine. The use of a heatpipe receiver greatly enhances system efficiency and potential life span. One issue that is raised during the design phase of heatpipe receivers is the potential solubility corrosion of the Stirling engine heat input section by the liquid metal working fluid. This Phase 1 effort initiated a program to evaluate and demonstrate coatings, applied to nickel based Stirling engine heater head materials, that are practically 'insoluble' in sodium, potassium, and NaK. This program initiated a study of nickel aluminide as a coating and developed and demonstrated a heatpipe test vehicle that can be used to test candidate materials and coatings. Nickel 200 and nickel aluminide coated Nickel 200 were tested for 1000 hours at 800 C at a condensation heat flux of 25 W/sq cm. Subsequent analyses of the samples showed no visible sign of solubility corrosion of either coated or uncoated samples. The analysis technique, photomicrographs at 200X, has a resolution of better than 2.5 microns (.0001 in). The results indicate that the heatpipe environment is not directly

Full Text Available The paper presents the results of experimental research of orientation effect on heat transfer characteristics of a pulsating heatpipe (PHP. It is shown that transport of either mass or heat depends on PHP orientation against it`s axis. As a consequence of comparing experimental data with other authors’ results it was concluded that PHP thermal resistance depends not only on orientation but on some other determinal factors such as device construction and thermophysical properties of heat carrier.

Full Text Available Given article presents experimental research of heat transfer characteristics of the pulsating heatpipe (PHP which consists of seven coils with 1 mm inner diameter. Water was used as the heat carrier. PHP construction, measuring circuit and research technique are presented. It is shown that under PHP functioning there are two characteristic modes of operation, which can be distinguished by values of thermal resistance. PHP heat exchange features are disclosed.

Full Text Available A comparison of heat transfer efficiency between the heatpipe and tube bundles heat exchanger is made based on heat transfer principle and the analysis of thermal characteristics. This paper argues that although heatpipe has the feature of high axial thermal conductivity, to those cases where this special function of heat transfer is unnecessary, heatpipe exchanger is not a high efficient heat exchanger when it is just used as a conventional heat exchanger in the industrial fields. In turn, there are some deficiencies for heatpipe exchanger, such as complicated manufacturing process, critical requirements for manufacturing materials, etc. which leads to a higher cost in comparison to a tubular heat exchanger. Nonetheless, due to its diverse structural features and extraordinary properties, heatpipe exchanger still has wide applications on special occasions.

To maximize the capacity of a nonarterial heatpipe, a wick is considered whose porosity is allowed to vary axially along its length. At every axial location the porosity is set no lower than required to maintain the wick in a nearly saturated state under the maximum heat-transport rate. The result is a wick whose permeability is everywhere as high as possible. The differential equation that governs the optimum porosity variation is solved numerically between a condenser-end boundary condition that just prevents a liquid slug or puddle in the vapor spaces and an evaporator-end boundary condition that just prevents circumferential groove dry-up. Experimental performance measurements for an ammonia heatpipe are presented.

Full Text Available The heatpipe is a novel heat transfer device to transfer large amount of heat through a small cross sectional area with very small temperature differences and it also posses high thermal conductance and low thermal impedance. In this paper, the heatpipe working parameters are analyzed using Taguchi methodology. The Taguchimethod is used to formulate the experimental work, analyze the effect of working parameters of the heatpipe and predict the optimal parameter of heatpipe such as heat input, inclination angle and flow rate. It is found that these parameters have a significant influence on heatpipe performance. The analysis of the Taguchi method reveals that, all the parameters mentioned above have equal contributions in the performance of heatpipe efficiency, thermal resistance and overall heat transfer coefficient. Experimental results are provided to validate the suitability of the proposed approach.

Full Text Available Heatpipe is device working with phase changes of working fluid inside hermetically closed pipe at specific pressure. The phase changes of working fluid from fluid to vapour and vice versa help heatpipe to transport high heat flux. The article deal about gravity heatpipe construction and processes casing inside during heatpipe operation. Experiment working fluid flow visualization is performed with two glass heatpipes with different inner diameter (13 mm and 22 mm and filled with water. The working fluid flow visualization explains the phenomena as a working fluid boiling, nucleation of bubbles, and vapour condensation on the wall, vapour and condensate flow interaction, flow down condensate film thickness on the wall occurred during the heatpipe operation.

Heatpipe is device working with phase changes of working fluid inside hermetically closed pipe at specific pressure. The phase changes of working fluid from fluid to vapour and vice versa help heatpipe to transport high heat flux. The article deal about gravity heatpipe construction and processes casing inside during heatpipe operation. Experiment working fluid flow visualization is performed with two glass heatpipes with different inner diameter (13 mm and 22 mm) and filled with water. The working fluid flow visualization explains the phenomena as a working fluid boiling, nucleation of bubbles, and vapour condensation on the wall, vapour and condensate flow interaction, flow down condensate film thickness on the wall occurred during the heatpipe operation.

Full Text Available In this research, heatingpipe was used in the solar collector in order to take better advantage of the solar energy. The energy obtained from the sun was transferred to the drying air by means of heatingpipes and this hot air was blown on the material to be dried. The water on the material to be dried vaporised with the effect of the hot air and drying took place. Because drying took place in the shade, distant from the direct radiation effects of the sun, some of the disadvantages seen in drying outside, under the sun were eliminated. Additionally, it was observed that it took less time to dry in this method than it takes to dry under the open sun.

An all weather heatpipe solar water heater (AWSWAH) comprising a collector of 4 m/sup 2/ (43 ft/sup 2/) and a low profile water tank of 160 liters (42 gal.) was developed. A single heatpipe consisting of 30 risers and two manifolds in the evaporator and a spiral condenser was incorporated into the AWSWAH. Condensate metering was done by synthetic fiber wicks. The AWSWAH was tested alongside two conventional solar water heaters of identical dimensions, an open loop system and a closed loop system. It was found that the AWSWAH was an average of 50% more effective than the open system in the temperature range 30-90 /sup 0/C (86-194 /sup 0/F). The closed loop system was the least efficient of the three systems.

A scheme is described for the recovery of waste heat from stacks of gas turbine engines and the utilization of recovered energy for the cooling of ambient air. Relationships are summarized for the modeling of components of the cooling system. Samples are presented from performance data that is predicted by the model. Effect of size and design of system components, as well as operational variables on system performance, are discussed. It is concluded that the single most significant variable in the design of the looped heat-pipe recovery and utilization system is the geometry of the exhaust pipe of the gas turbine engine. (author)

This paper focuses on the heat transfer performance of semi-open heatpipe which is a new type of heatpipe. After analyzing its condensation heat transfer mechanisms theoretically, several semi-open heatpipes in different length ratios and upper hole diameters are studied experimentally and compared with the same dimensions closed heatpipes. Experimental results show that the heat transfer performance of semi-open heatpipe becomes better by increasing heat transfer rate. At the first transitional point, the heat transfer performance of semi-open heatpipe approaches the level of the closed heatpipe. It is suitable to choose upper small hole about 1 mm in diameter and length ratio larger than 0.6 for the semi-open heatpipe.

A novel cryogenic heatpipe, oscillating heatpipe (OHP), which consists of an 4 × 18.5 cm evaporator, a 6 × 18.5 cm condenser, and 10 cm length of adiabatic section, has been developed and experimental characterization conducted. Experimental results show that the maximum heat transport capability of the OHP reached 380W with average temperature difference of 49 °C between the evaporator and condenser when the cryogenic OHP was charged with liquid nitrogen at 48% (v/v) and operated in a horizontal direction. The thermal resistance decreased from 0.256 to 0.112 while the heat load increased from 22.5 to 321.8 W. When the OHP was operated at a steady state and an incremental heat load was added to it, the OHP operation changed from a steady state to an unsteady state until a new steady state was reached. This process can be divided into three regions: (I) unsteady state; (II) transient state; and (III) new steady state. In the steady state, the amplitude of temperature change in the evaporator is smaller than that of the condenser while the temperature response keeps the same frequency both in the evaporator and the condenser. The experimental results also showed that the amplitude of temperature difference between the evaporator and the condenser decreased when the heat load increased. PMID:20585410

The modeling work described herein represents Sandia National Laboratories (SNL) portion of a collaborative three-year project with Northrop Grumman Electronic Systems (NGES) and the University of Missouri to develop an advanced, thermal ground-plane (TGP), which is a device, of planar configuration, that delivers heat from a source to an ambient environment with high efficiency. Work at all three institutions was funded by DARPA/MTO; Sandia was funded under DARPA/MTO project number 015070924. This is the final report on this project for SNL. This report presents a numerical model of a pulsating heatpipe, a device employing a two phase (liquid and its vapor) working fluid confined in a closed loop channel etched/milled into a serpentine configuration in a solid metal plate. The device delivers heat from an evaporator (hot zone) to a condenser (cold zone). This new model includes key physical processes important to the operation of flat plate pulsating heatpipes (e.g. dynamic bubble nucleation, evaporation and condensation), together with conjugate heat transfer with the solid portion of the device. The model qualitatively and quantitatively predicts performance characteristics and metrics, which was demonstrated by favorable comparisons with experimental results on similar configurations. Application of the model also corroborated many previous performance observations with respect to key parameters such as heat load, fill ratio and orientation.

The modeling work described herein represents Sandia National Laboratories (SNL) portion of a collaborative three-year project with Northrop Grumman Electronic Systems (NGES) and the University of Missouri to develop an advanced, thermal ground-plane (TGP), which is a device, of planar configuration, that delivers heat from a source to an ambient environment with high efficiency. Work at all three institutions was funded by DARPA/MTO; Sandia was funded under DARPA/MTO project number 015070924. This is the final report on this project for SNL. This report presents a numerical model of a pulsating heatpipe, a device employing a two phase (liquid and its vapor) working fluid confined in a closed loop channel etched/milled into a serpentine configuration in a solid metal plate. The device delivers heat from an evaporator (hot zone) to a condenser (cold zone). This new model includes key physical processes important to the operation of flat plate pulsating heatpipes (e.g. dynamic bubble nucleation, evaporation and condensation), together with conjugate heat transfer with the solid portion of the device. The model qualitatively and quantitatively predicts performance characteristics and metrics, which was demonstrated by favorable comparisons with experimental results on similar configurations. Application of the model also corroborated many previous performance observations with respect to key parameters such as heat load, fill ratio and orientation.

loss from an ideally insulated pipe connected to the top of a hot water tank is mainly due to a natural convection flow in the pipe, that the heat loss coefficient of pipes connected to the top of a hot water tank is high, and that a heat trap can reduce the heat loss coefficient significantly. Further......The heat loss from pipe connections at the top of hot water storage tanks with and without a heat trap is investigated theoretically and compared to similar experimental investigations. Computational Fluid Dynamics (CFD) is used for the theoretical analysis. The investigations show that the heat...

loss from an ideally insulated pipe connected to the top of a hot water tank is mainly due to a natural convection flow in the pipe, that the heat loss coefficient of pipes connected to the top of a hot water tank is high, and that a heat trap can reduce the heat loss coefficient significantly. Further......The heat loss from pipe connections at the top of hot water storage tanks with and without a heat trap is investigated theoretically and compared to similar experimental investigations. Computational Fluid Dynamics (CFD) is used for the theoretical analysis. The investigations show that the heat...

The authors summarize the results of detailed neutronic and thermal-hydraulic evaluations of the heatpipe cooled thermionic (HPTI) reactor design, identify its key design attributes, and quantify its performance characteristics. The HPTI core uses modular, liquid-metal core heat transfer assemblies to replace the liquid-metal heat transport loop employed by in-core thermionic reactor designs of the past. The nuclear fuel, power conversion, heat transport, and heat rejection functions are all combined into a single modular unit. The reactor/converter assembly uses UN fuel pins to obtain a critical core configuration with in-core safety rods and reflector controls added to complete the subassembly. By thermally bonding the core heat transfer assemblies during the reactor core is coupled neutronically, thermally, and electrically into a modular assembly of individual power sources with cross-tied architecture. A forward-facing heatpipe radiator assembly extends from the reactor head in the shape of a frustum of a cone on the opposite side of the power system from the payload. Important virtues of the concept are the absence of any single-point failures and the ability of the core to effectively transfer the TFE waste heat load laterally to other in-core heat transfer assemblies in the event of multiple failures in either in-core and radiator heatpipes.

The authors summarize the results of detailed neutronic and thermal-hydraulic evaluations of the heatpipe cooled thermionic (HPTI) reactor design, identify its key design attributes, and quantify its performance characteristics. The HPTI core uses modular, liquid-metal core heat transfer assemblies to replace the liquid-metal heat transport loop employed by in-core thermionic reactor designs of the past. The nuclear fuel, power conversion, heat transport, and heat rejection functions are all combined into a single modular unit. The reactor/converter assembly uses UN fuel pins to obtain a critical core configuration with in-core safety rods and reflector controls added to complete the subassembly. By thermally bonding the core heat transfer assemblies during the reactor core is coupled neutronically, thermally, and electrically into a modular assembly of individual power sources with cross-tied architecture. A forward-facing heatpipe radiator assembly extends from the reactor head in the shape of a frustum of a cone on the opposite side of the power system from the payload. Important virtues of the concept are the absence of any single-point failures and the ability of the core to effectively transfer the TFE waste heat load laterally to other in-core heat transfer assemblies in the event of multiple failures in either in-core and radiator heatpipes.

An improved passive cooling arrangement is disclosed for maintaining adjacent or related components of a nuclear reactor within specified temperature differences. Specifically, heatpipes are operatively interposed between the components, with the vaporizing section of the heatpipe proximate the hot component operable to cool it and the primary condensing section of the heatpipe proximate the other and cooler component operable to heat it. Each heatpipe further has a secondary condensing section that is located outwardly beyond the reactor confinement and in a secondary heat sink, such as air ambient the containment, that is cooler than the other reactor component. By having many such heatpipes, an emergency passive cooling system is defined that is operative without electrical power.

The main topics of article are construction of loop heatpipe, thermal visualization of working fluid dynamics and research results interpretation. The work deals about heat flux transport by working fluid in loop heatpipe from evaporator to condenser evolution. The result of the work give us how the hydrodynamic and thermal processes which take place inside the loop of heatpipe affect on the overall heat transport by loop heatpipe at start-up and during operation.

Full Text Available The main topics of article are construction of loop heatpipe, thermal visualization of working fluid dynamics and research results interpretation. The work deals about heat flux transport by working fluid in loop heatpipe from evaporator to condenser evolution. The result of the work give us how the hydrodynamic and thermal processes which take place inside the loop of heatpipe affect on the overall heat transport by loop heatpipe at start-up and during operation.

Seperated heatpipe systems are widely used in the fields of waste heat recovery and air conditioning due to their high heat transfer capability,and optimization of heat transfer process plays an important role in high-efficiency energy utilization and energy conservation.In this paper,the entransy dissipation analysis is conducted for the separated heatpipe system,and the result indicates that minimum thermal resistance principle is applicable to the optimization of the separated heatpipe system.Whether in the applications of waste heat recovery or air conditioning,the smaller the entransy-dissipation-based thermal resistance of the separated heatpipe system is,the better the heat transfer performance will be.Based on the minimum thermal resistance principle,the optimal area allocation relationship between evaporator and condenser is deduced,which is numerically verified in the optimation design of separated heatpipe system.

For the design and operation of nuclear power plants the Leak-Before-Break (LBB) behavior of a piping component has to be shown. This means that the length of a crack resulting in a leak is smaller than the critical crack length and that the leak is safely detectable by a suitable monitoring system. The LBB-concept of Siemens/KWU is based on computer codes for the evaluation of critical crack lengths, crack openings, leakage areas and leakage rates, developed by Siemens/KWU. In the experience with the leak rate program is described while this paper deals with the computation of crack openings and leakage areas of longitudinal and circumferential cracks by means of fracture mechanics. The leakage areas are determined by the integration of the crack openings along the crack front, considering plasticity and geometrical effects. They are evaluated with respect to minimum values for the design of leak detection systems, and maximum values for controlling jet and reaction forces. By means of fracture mechanics LBB for subcritical cracks has to be shown and the calculation of leakage areas is the basis for quantitatively determining the discharge rate of leaking subcritical through-wall cracks. The analytical approach and its validation will be presented for two examples of complex structures. The first one is a pipe branch containing a circumferential crack and the second one is a pipe bend with a longitudinal crack.

A scheme is described for the recovery of waste heat from stacks of gas turbine engines by means of heat-pipe loops. The recovered energy is supplied to an absorption chiller that cools the intake air of the gas turbine engine to enhance its performance. Mathematical expressions are introduced which accurately portray existing tabulated thermophysical properties data for those variables needed during the modelling of the system. (author)

Numerous heatpipes were designed, manufactured, and filled on a specially developed filling rig. Each heatpipe was incorporated into a prototype solar water heater developed for this purpose, and was tested under actual insolation conditions. An extensive testing program lasting for more than a year revealed that the heatpipes perform satisfactorily as heat transfer elements in solar water heaters. A special heatpipe featuring a compact and effective condenser configuration was also tested. It was observed to likewise exhibit isothermal behavior and hence promised potential for large scale solar applications.

Five advanced heatpipe systems utilizing phase changing heat transfer concept are introduced, which are; a separate type heatpipeheat exchanger, a heatpipe turbine, micro heatpipes, a thermocapillary loop system and mass-produced tubes with inner fin. Inside of these heatpipes, contrary to the conventional heat transfer tubes, evaporation and condensation processes are heavily influenced by the surface tension effect. This effect is also dominant in the heatpipes operating under micro-...

Full Text Available Thermotechnical characteristics of heatpipes are considered as high-efficient heat-transfer devices, which can provide energy-saving technologies for heat supply and ventilating systems and for different branches of industry. Thermotechnical and working (”performance capability” characteristics of heatpipes are investigated. By ”performance capability” of heatpipes and heat-transfer devices on heatpipes we mean the system state, where it can perform set functions and keep parameter values (thermal power, conductivity, thermal resistance, heat-transfer coefficient, temperature level and differential, etc. within the regulations of standardized specifications. The article presents theoretical and experimental methods of «gaslock» length determination on noncondensable gases during long-lasting tests of ammonia heatpipes made of aluminum shape АS – КRА 7.5 – R1 (alloy АD – 31. The paper gives results of research of thermotechnical characteristics of heatpipes in horizontal and vertical states (separate and as a set part while using different systems of thermal insulation. The obtained results of thermotechnical and resource tests show the advantages of ammonia heatpipes as basic elements for heat exchanger design in heating and ventilation systems.

Performance heatpipes depends on several parameters. This article deals with the performance of heatpipes, depending on the working fluid and operating temperature. There is described the essential function of the heatpipe manufacturing process. Stainless heatpipes were made of material AISI 304 and filled with a distilled water and solution of distilled water with silver nitrate, up to 20% of the heatpipe inner volume. Measurements were carried at an operating temperature of 40 °C to 90 °C. The performance was measured on the experimental device. Presented results show the progress of individual measurements and the effect of operating parameters and working fluid on the performance of heatpipes.

The development of a jet pump assisted arterial heatpipe is described. The concept utilizes a built-in capillary driven jet pump to remove vapor and gas from the artery and to prime it. The continuous pumping action also prevents depriming during operation of the heatpipe. The concept is applicable to fixed conductance and gas loaded variable conductance heatpipes. A theoretical model for the jet pump assisted arterial heatpipe is presented. The model was used to design a prototype for laboratory demonstration. The 1.2 m long heatpipe was designed to transport 500 watts and to prime at an adverse elevation of up to 1.3 cm. The test results were in good agreement with the theoretical predictions. The heatpipe carried as much as 540 watts and was able to prime up to 1.9 cm. Introduction of a considerable amount of noncondensible gas had no adverse effect on the priming capability.

Highlights: • Entropy generation of heatpipe with nanofluid has been studied. • Nanofluid has significant effect on heatpipe performance. • Entropy generation in heatpipe decreases when nanofluids are used as working fluids. - Abstract: Thermal performance of cylindrical heatpipe with nanofluid is studied based on the laws of thermodynamics. The objective of the present work is to investigate nanofluids effect on different sources of entropy generation in heatpipe caused by heat transfer between hot and cold reservoirs and also frictional losses and pressure drop in the liquid and vapor flow along heatpipe. An analytical study was performed to formulate all sources of entropy generation and the predicted results are compared with experimental ones. Cylindrical miniature grooved heatpipes of 250 mm length and 6.35 mm outer diameter were fabricated and tested with distilled water and water based TiO{sub 2} and Al{sub 2}O{sub 3} nanofluids at different concentrations as working fluids. Analytical and experimental results revealed that the entropy generation in heatpipes decreases when nanofluids are used as working fluids instead of basefluid which results in improved thermal performance of the heatpipes with nanofluids.

The introduction of district heating has reduced the environmental impact from local heat production in urban areas. However, in order to fit into a sustainable society, district heating must be continuously developed according to the increasing demands on activities in a society moving towards sustainability. Our technical improvements must result in environmental improvements. This thesis focuses on the environmental performance of the distribution system - the district heatingpipes. The purpose of this research is to understand how the distribution system can be improved. The information presented in this thesis can be used to identify possibilities for improving the environmental performance of different life cycle phases of the distribution system as well as a baseline when evaluating new technical developments. The heat losses during use of the pipes are of large importance for the environmental impact of district heatingpipes. Such heat losses can be modelled if the mass transfer parameters for gases in the polyurethane insulation and the polyethylene casing are known. The diffusion coefficients, the permeability coefficients and the solubility coefficients and their temperature dependence have been determined for cyclopentane, carbon dioxide, nitrogen, and oxygen. The same parameters have been studied for the blowing agent alternative HFC-365mfc at room temperature. The long-term thermal performance of district heatingpipes has been modelled using effective permeabilities for the pipe construction. Environmental consequences of heat losses during the use phase of district heatingpipes have been compared with the impacts from production of the pipes and from construction of the district heating network. The use of the district heatingpipes is the most important of the studied life cycle phases. Thus, it is very important to minimise heat losses from the pipes. The heat losses will for some district heatingpipes increase notably during use due to foam

A promising approach to energy conservation is the use of heatpipes to recover heat now lost in effluent processing wastewater streams. At Radford Army Ammunition Plant a prototype water-to-water heatpipeheat exchanger (HPHX) was evaluated. Heat was extracted from wastewater and recovered heat then used to preheat incoming fresh water. The heatpipe is schematicized. Design objectives--access to wasterwater section, provision for periodic inspection--are specified. Based on these objectives the HPHX design is shown. A performance analysis is carried out by means of equations. Based on mobilization rates at Radford, a savings of significant amount will be realized.

Heatpipes are used in spacecraft to equalize the temperature of structures and maintain temperature control of electronic components. Information is provided for a designer on: (1) a typical mounting technique, (2) choices available in wick geometries and fluids, (3) tests involved in flight-qualifying the design, and (4) heatpipe limitations. An evaluation of several heatpipe designs showed that the behavior of heatpipes at room temperature does not necessarily correlate with the classic equations used to predict their performance. They are sensitive to such parameters as temperature, fluid inventory, orientation, and noncondensable gases.

National Aeronautics and Space Administration — This Small Business Innovation Research project will develop Pressure Controlled HeatPipes (PCHPs) for precise temperature control (milli-Kelvin level). Several...

The thermal resistance of conventional heatpipes increases over the capillary limit because of the insufficient supplement of the working fluid. Due to the shortage of the liquid supplement, thermosyphon is widely used for vertically oriented heat transport and high heat load conditions. Thermosyphons are two-phase heat transfer devices that have the highly efficient heat transport from evaporation to condensation section that makes an upward driving force for vapor. In the condenser section, the vapor condenses and releases the latent heat. Due to the gravitation force acting on the liquid in the tube, working fluid back to the evaporator section, normally this process operate at the vertical and inclination position. The use of two-phase closed thermosyphon (TPCT) for the cooling devices has the limitation due to the phase change of the working fluid assisted by gravity force. Due to the complex phenomenon of two-phase flow, it is required to understand what happened in TPCT. The visualization of the thermosyphon and heatpipe is investigated for the decrease of thermal resistance and enhancement of operation limit. Weibel et al. investigated capillary-fed boiling of water with porous sintered powder wick structure using high speed camera. At the high heat flux condition, dry-out phenomenon and a thin liquid film are observed at the porous wick structure. Wong and Kao investigated the evaporation and boiling process of mesh wicked heatpipe using optical camera. At the high heat flux condition, the water filing became thin and partial dry-out was observed in the evaporator section. Our group suggested the concept of a hybrid heatpipe with control rod as Passive IN-core Cooling System (PINCs) for decay heat removal for advanced nuclear power plant. The hybrid heatpipe is the combination of the heatpipe and control rod. It is necessary for PINCs to contain a neutron absorber (B{sub 4}C) to have the ability of reactivity control. It has annular vapor space and

The use of heatpipes is being considered as a means of reducing the peak temperature and large thermal gradients at the leading edges of reentry vehicles and hypersonic aircraft and in nuclear reactors. In the basic cooling concept, the heatpipe covers the leading edge, a portion of the lower wing surface, and a portion of the upper wing surface. Aerodynamic heat is mainly absorbed at the leading edge and transported through the heatpipe to the upper and lower wing surface, where it is rejected by thermal radiation and convection. Basic governing equations are written to determine the startup, transient, and steady state performance of a haet pipe which has initially frozen alkali-metal as the working fluid.

At the Hamaoka Nuclear Power Station Unit-1 (540 MWe of electric output; BWR-4 type) of the Chubu Electric Power Co., Ltd., an incident of pipe rupture of residual heat removal system on steam condenser system occurred on November, 2001. This incident gave no effects on outer parts of the station, because safety system apparatuses in the station worked adequately from a standpoint of accidental phenomenon. On the other hand, on its forming processes, as it is no similar case at the nuclear power stations in and out of Japan, to securely carry out countermeasures for preventing a recurrence of the incidence, its cause was striven to elucidate thoroughly. This paper was introduced about contents and results on site surveys, and surveys such as tests, analysis, and so on performed for about a half year after the incident, for preventing a recurrence of similar incidents. (G.K.)

Rotating and revolving heatpipes have been used in a variety of applications including heatpipeheat exchangers, cooling of rotating electrical machines, and heat removal in high speed cutting operations. The use of heatpipes in rotating environments has prompted many analytical, numerical, and experimental investigations of the heat transfer characteristics of these devices. Past investigations, however, have been restricted to the study of straight heatpipes. In this work, a curved rotating heatpipe is studied numerically and experimentally. In certain types of rotating machines, heat generating components, which must be cooled during normal operation, are located at some radial distance from the axis of rotation. The bent heatpipe studied here is shown to have advantages when compared to the conventional straight heatpipes in these off-axis cooling scenarios. The heatpipe studied here is built so that both the condenser and evaporator sections are parallel to the axis of rotation. The condenser section is concentric with the axis of rotation while the evaporator section can be placed in contact with off-axis heat sources in the rotating machine. The geometry is achieved by incorporating an S-shaped curve between the on-axis rotating condenser section and the off-axis revolving evaporator section. Furthermore, the heatpipe uses an annular gap wick structure. Incorporating an annular gap wick structure into the heatpipe allows for operation in a non-rotating environment. A numerical model of this rotating heatpipe is developed. The analysis is based on a two-dimensional finite-difference model of the liquid flow coupled to a one-dimensional model of the vapor flow. Although the numerical model incorporates many significant aspects of the fluid flow, the flow in the actual heatpipe is expected to be threedimensional. The rotating heatpipe with the S-shaped curve is also studied experimentally to determine how well the numerical model captures the key

This paper investigates the enhancement of heat transfer coefficient and Nusselt number of a nanofluid containing nanoparticles (γ-AL2O3) with a particle size of 20 nm and volume fraction of 0.1%-0.3% (V/V). Effects of temperature and concentration of nanoparticles on Nusselt number changes and heat transfer coefficient in a double pipeheat exchanger with counter turbulent flow are investigated. Comparison of experimental results with valid theoretical data based on semiempirical equations shows an acceptable agreement. Experimental results show a considerable increase in heat transfer coefficient and Nusselt number up to 19%-24%, respectively. Also, it has been observed that the heat transfer coefficient increases with the operating temperature and concentration of nanoparticles.

The superior heat transfer capability, structural simplicity, relatively inexpensive, insensitivity to the gravitational field, silence and reliability are some of its outstanding features. We study about heat transfer equation of heatpipe and program predicting performance which is considering geometrical shape of heatpipe by the related heat transfer equation of heatpipe. The operating temperature is 450 .deg. C - 950 .deg. C, working fluid is sodium, material for container is stainless steel, and type of wick is sintered metal. As a result of evaluating program about performance of circular sodium heatpipe based on MATLAB code, express correlation between radius and LHR, correlation between heat transfer length and LHR, correlation between wick and LHR, correlation between operating temperature and LHR. Generally radius values of heatpipe are proportional to LHR because of increase of mass flow which is main factor of heat flow. Heat transfer length values of heatpipe are inversely proportional to LHR and slightly inversely proportional to heat rate. Pore size is proportional to LHR. Although increase of pore size decrease capillary pressure, decrease more pressure drop in liquid phase. As a result, mass flow and heat rate are increase. But we have to do additional consideration about pore size and voidage in the aspect of safety and production technique.

Full Text Available This research was to study the comparisons of heat transfer performance of closed-looped oscillating heatpipe and closed-looped oscillating heatpipe with check valves heat exchangers with R134a, Ethanol and water were used as the working fluids. A set of heatpipeheat exchanger (CLOHP and CLOHP/CV were made of copper tubes in combination of following dimension: 2.03 mm inside diameter: 40 turns, with 20, 10 and 20 cm for evaporator, adiabatic and condenser sections lengths. The working fluid was filled in the tube at the filling ratio of 50%. The evaporator section was given heat by heater while the condenser section was cooled by air. The adiabatic section was properly insulated. In the test operation, it could be concluded as follows. It indicated that the heat transfer performance of closed-looped oscillating heatpipe with check valves heat exchanger better than closed-looped oscillating heat exchanger.

The Moderated HeatPipe Thermionic Reactor (MOHTR) thermionic space reactor design combines the low risk technology associated with the Thermionic Fuel Element (TFE) Verification Program with the high reliability heat transfer capability of liquid metal heatpipe technology. The resulting design concept, capable of implementation over the power range of 10 to 100 kWe, offers efficiency and reliability with reduced risk of single point failures. The union of TFE and heatpipe technology is achieved by imbedding TFEs and heatpipes in a beryllium matrix to which they are thermally coupled by brazing or by liquid metal (NaK or Na) bonding. The reactor employs an array of TFE modules, each comprising a TFE, a zirconium hydride (ZrH) cylinder for neutron moderation, and heatpipes for transport of heat from the collector surface of the TFE to the waste heat radiator. An advantage of the design is the low temperature drop from the collector surface to the radiating surface. This is a result of the elimination of electrical insulation from the heat transport path through electrical isolation of the modules. The module used in this study consisted of a beryllium core, and electrical cartridge heater simulating the TFE, and three heatpipes to dissipate the waste heat. The investigation was focused on the thermal performance of the assembly, including evaluation of the sodium and braze bonding options for minimizing the thermal resistance between the elements, the temperature distribution in the beryllium matrix, and the heatpipe performance. Continuing subjects of the investigation include performance of the heatpipes through start-up transients, during normal operation, and in a single heatpipe failure mode. Secondary objectives of the investigation include correlation of analytic models for the thermionic element and module including the effects of gap thermal conductances at the modules electrically insulated surfaces.

In improved apparatus, ampoule of material directionally solidified mounted in central hole of annular heatpipe, at suitable axial position between heated and cooled ends. Heated end held in fixed position in single-element furnace; other end left in ambient air or else actively cooled. Gradient of temperature made to move along heatpipe by changing pressure of noncondensable gas. In comparison with prior crystal-growing apparatuses, this one simpler, smaller, and more efficient.

Semi-open heatpipes were studied experimentally in this work. A new kind of semi-open heatpipe with fluid swirl backflow was developed on the basis of the traditional semi-open heatpipe. Heat transfer characteristics during operation and start-up of closed heat pipe、traditional semi-open heatpipe and swirl flow semi-open heatpipe were investigated. The swirl orifice' s backflow effect on enhancing the working limitation was obtained. Heat exchangers or waste heat boilers made of swirl flow semi-open heatpipes and semi-open heatpipes have been successfully used in high or variable gas temperature engineering applications.

An important plasma-facing component (PFC) in future nuclear fusion reactors is the so-called divertor which allows power exhaust and removal of impurities from the main plasma. The most highly loaded parts of a divertor are the target plates which have to withstand intense particle bombardment. This intense particle bombardment leads to high heat fluxes onto the target plates which in turn lead to severe thermomechanical loads. With regard to future nuclear fusion reactors, an improvement of the performance of divertor targets is desirable in order to ensure reliable long term operation of such PFCs. The performance of a divertor target is most closely linked to the properties of the materials that are used for its design. W fibre-reinforced Cu (Wf/Cu) composites are regarded as promising heat sink materials in this respect. These materials do not only feature adequate thermophysical and mechanical properties, they do also offer metallurgical flexibility as their microstructure and hence their macroscopic properties can be tailored. The contribution will point out how Wf/Cu composites can be used to realise an advanced design of a divertor target and how these materials can be fabricated by means of liquid Cu infiltration.

SuperCritical-Water-cooled Reactors (SCWRs) are being developed as one of the Generation-IV nuclear-reactor concepts. SuperCritical Water (SCW) Nuclear Power Plants (NPPs) are expected to have much higher operating parameters compared to current NPPs, i.e., pressure of about 25 MPa and outlet temperature up to 625 °C. This study presents the heat transfer analysis of an intermediate Heat exchanger (HX) design for indirect-cycle concepts of Pressure-Tube (PT) and Pressure-Vessel (PV) SCWRs. Thermodynamic configurations with an intermediate HX gives a possibility to have a single-reheat option for PT and PV SCWRs without introducing steam-reheat channels into a reactor. Similar to the current CANDU and Pressurized Water Reactor (PWR) NPPs, steam generators separate the primary loop from the secondary loop. In this way, the primary loop can be completely enclosed in a reactor containment building. This study analyzes the heat transfer from a SCW primary (reactor) loop to a SCW and Super-Heated Steam (SHS) secondary (turbine) loop using a double-pipe intermediate HX. The numerical model is developed with MATLAB and NIST REFPROP software. Water from the primary loop flows through the inner pipe, and water from the secondary loop flows through the annulus in the counter direction of the double-pipe HX. The analysis on the double-pipe HX shows temperature and profiles of thermophysical properties along the heated length of the HX. It was found that the pseudocritical region has a significant effect on the temperature profiles and heat-transfer area of the HX. An analysis shows the effect of variation in pressure, temperature, mass flow rate, and pipe size on the pseudocritical region and the heat-transfer area of the HX. The results from the numerical model can be used to optimize the heat-transfer area of the HX. The higher pressure difference on the hot side and higher temperature difference between the hot and cold sides reduces the pseudocritical-region length, thus

Work performed by Dynatherm Corporation for Teledyne Isotopes during a program entitled ''HeatPipe Fabrication, Associated Technical Support and Reporting'' is reported. The program was initiated on November 29, 1972; the main objectives were accomplished with the delivery of the heatpipes for the HPG. Life testing of selected heatpipe specimens is continuing to and beyond the present date. The program consisted of the following tasks: HeatPipe Development of Process Definition; Prototype HeatPipes for Fin Segment Test; HPG HeatPipe Fabrication and Testing; Controlled HeatPipe Life Test; and HeatPipe Film Coefficient Determination. (TFD)

The induction heating bent pipes of carbon steel welded pipes are used for the piping in nuclear power plants, in place of elbows. This application is useful to suppress the radiation exposure at in-service inspection. The quality of the bent pipes are controlled on the technical standards of welding for electrical equipments. However, the influence of the bending condition has not been yet sufficiently understood on the mechanical properties of the bent pipes. The purpose of this investigation is to establish the appropriate bending condition for the carbon steel weld pipe which corresponds to the carbon steel pipe STPT 42 in JIS G 3456, in relation to the transformation of the structures of the base metal and the weld metal during bending. The results are summarized as follows: (1) The maximum heating temperature should be set in the range from 900 deg C to 1000 deg C, in order to assure the high Charpy impact properties. (2) The maximum heating temperature which is lower than 900 deg C causes the imperfect transformation of the base metal and the weld metal, then is likely to spoil the Charpy impact properties. (3) Higher heating rate causes the increase of A/sub c1/ point, remarkably for the base metal which has higher carbon content than weld metal. (4) Higher cooling rate causes hardening of the base metal and weld metal, however, the transformation temperature does not change remarkably, except for the Ar/sub 1/ point of base metal.

The use of high-temperature heatpipes has been proposed for cooling the leading edges and nose cones of re-entry vehicles, rail guns, and laser mirrors, as well as for the thermal management of future hypersonic vehicle structures. The startup behavior of high temperature heatpipes from the frozen state was investigated both numerically and experimentally for various heat loads and input locations. A high temperature sodium/stainless steel heatpipe with multiple heat sources and sinks was fabricated, processed, and tested. A numerical simulation of the transient heatpipe performance including the vapor region, wick structure, and the heatpipe wall is given. Furthermore, experimental and numerical analyses of several operating parameters of a low-temperature copper-water heatpipe under uniform circumferential heating and block heating has been performed. Finally, a numerical analysis of transient heatpipe performance including nonconventional heatpipes with nonuniform heat distributions is presented. Numerical calculations were then made for a leading edge heatpipe with localized high heat fluxes.

An improved heatpipe design using separately connected two-section one-way flow heatpipes with internal microgrooves instead of wicks is described. This design is now commercially available for use to increase the dehumidification capacity of air conditioning systems. The design also includes a method of introducing fresh air into buildings while recovering heat and controlling the humidity of the incoming air. Included are applications and case studies, load calculations and technical data, and installation, operation, and maintenance information.

Developing clean energy and utilizing waste energy has become increasingly vital. Research targeting the advancement of thermally powered adsorption cooling technologies has progressed in the past few decades, and the awareness of fuel cells and thermally activated (heatpipeheat exchangers) adsorption systems using natural refrigerants and/or alternatives to hydrofluorocarbon-based refrigerants is becoming ever more important. HeatPipes and Solid Sorption Transformations: Fundamentals and Practical Applications concentrates on state-of-the-art adsorption research and technologies for releva

Based on the thermal requirements of the future telecommunication satellites, the development of a High Capacity Grooved HeatPipe (HPG), was contracted by ESA to SABCA leading to an aluminium extruded heatpipe (outer diameter of 25 mm) based on a multi re-entrant grooves design. After an intensive acceptance test campaign whose results showed a good confidence in the design and the fulfillment of the required specifications of heat transport and on tilt capability (experimental maximum heat transport capability of 1500 Watt metres for a vapour temperature of 20 deg C), similar heatpipes have been developed with various outer diameters (11 mm, 15 mm and 20 mm) and with various shapes (circular outer shapes, integrated saddles). Several of these heatpipes were tested during two parabolic flight campaigns, by varying the heat loads during the micro-gravity periods. This HGP heatpipe family is now being submitted to a space qualification program according to ESA standards (ESA PSS-49), both in straight and bent configuration. Within this qualification, the heatpipes are submitted to an extended test campaign including environmental (random/sinus vibration, constant acceleration) and thermal tests (thermal performance, thermal cycle, thermal soak, ageing). (authors) 9 refs.

Full Text Available This paper discuses the use of self rewetting fluids in the heatpipe. In conventional heatpipes, the working fluid used has a negative surface-tension gradient with temperature. It is an unfavourable one and it decreases the heat transport between the evaporator section and the condenser section. Self rewetting fluids are dilute aqueous alcoholic solutions which have the number of carbon atoms more than four. Unlike other common liquids, self-rewetting fluids have the property that the surface tension increases with temperature up to a certain limit. The experiments are conducted to improve the heat-transport capability and thermal efficiency of capillary assisted heatpipes with the self rewetting fluids like aqueous solutions of n-Butanol and n-Pentanol and its performance is compared with that of pure water. The n-Butanol and n-Pentanol are added to the pure water at a concentration of 0.001moles/lit to prepare the self rewetting fluids. The heatpipes are made up of copper container with a two-layered stainless steel wick consisting of mesh wrapped screen. The experimental results show that the maximum heat transport of the heatpipe is enhanced and the thermal resistances are considerably decreased than the traditional heatpipes filled with water. The fluids used exhibit an anomalous increase in the surface tension with increasing temperature.

Light emitting diode (LED) cooling is facing the challenge of high heat flux more seriously with the increase of input power and diode density. The proposed unique thermosyphon heatpipeheat sink is particularly suitable for cooling of high power density LED chips and other electronics, which has a heat dissipation potential of up to 280 W within an area of 20 mm × 22 mm (>60 W/cm2) under natural air convection. Meanwhile, a thorough visualization investigation was carried out to explore the two phase flow characteristics in the proposed thermosyphon heatpipe. Implementing this novel thermosyphon heatpipeheat sink in the cooling of a commercial 100 W LED integrated chip, a very low apparent thermal resistance of 0.34 K/W was obtained under natural air convection with the aid of the enhanced boiling heat transfer at the evaporation side and the enhanced natural air convection at the condensation side.

An experimental study was carried out to investigate the effects of aqueous CuO nanofluids on thermal performance of a horizontal mesh heatpipe working at steady sub-atmospheric pressures. The nanofluid was composed of deionized water and CuO nanoparticles with an average diameter of 50 nm. The experimental results show that adding CuO nanoparticles into deionized water can significantly enhance heat transfer coefficients of both evaporator and condenser, and the maximum heat flux of the heatpipe. There is an optimal mass concentration of nanoparticles corresponding to the maximum heat transfer enhancement. The operating pressure has an apparent impact on both the evaporating and condensing heat transfer enhancements. The heat transfer enhancement effects increase distinctly with the decrease of the pressure. The present investigation discovers that the thermal performance of a mesh heatpipe can be evidently strengthened by substituting CuO nanofluids for deionized water under sub-atmospheric pressures. (author)

An experimental study was carried out to investigate the effects of aqueous CuO nanofluids on thermal performance of a horizontal mesh heatpipe working at steady sub-atmospheric pressures. The nanofluid was composed of deionized water and CuO nanoparticles with an average diameter of 50 nm. The experimental results show that adding CuO nanoparticles into deionized water can significantly enhance heat transfer coefficients of both evaporator and condenser, and the maximum heat flux of the heatpipe. There is an optimal mass concentration of nanoparticles corresponding to the maximum heat transfer enhancement. The operating pressure has an apparent impact on both the evaporating and condensing heat transfer enhancements. The heat transfer enhancement effects increase distinctly with the decrease of the pressure. The present investigation discovers that the thermal performance of a mesh heatpipe can be evidently strengthened by substituting CuO nanofluids for deionized water under sub-atmospheric pressures.

Loop heatpipes (LHP's) are two-phase heat transfer devices that utilize the evaporation and condensation of a working fluid to transfer heat, and the capillary forces developed in the porous wicks to circulate the fluid. The LHP was first developed in the former Soviet Union in the early 1980s, about the same time that the capillary pumped loop (CPL) was developed in the United States. The LHP is known for its high pumping capability and robust operation mainly due to the use of fine-pored metal wicks and an integral evaporator/hydro-accumulator design. The LHP technology is rapidly gaining acceptance in aerospace community. It is the baseline design for thermal control of several spacecraft, including NASA's GLAS and Chemistry, ESA's ATLID, CNES' STENTOR, RKA's OBZOR, and several commercial satellites. Numerous LHP papers have been published since the mid-1980's. Most papers presented test results and discussions on certain specific aspects of the LHP operation. LHP's and CPL's show many similarities in their operating principles and performance characteristics. However, they also display significant differences in many aspects of their operation. Some of the LHP behaviors may seem strange or mysterious, even to experienced CPL practitioners. The main purpose of this paper is to present a systematic description of the operating principles and thermal-hydraulic behaviors of LHP'S. LHP operating principles will be given first, followed by a description of the thermal-hydraulics involved in LHP operation. Operating characteristics and important parameters affecting the LHP operation will then be described in detail. Peculiar behaviors of the LHP, including temperature hysteresis and temperature overshoot during start-up, will be explained. For simplicity, most discussions will focus upon LHP's with a single evaporator and a single condenser, but devices with multiple evaporators and condensers will also be discussed. Similarities and differences between LHP's and

Design concepts for small Fission Power Systems (FPS) have shown that heatpipe cooled reactors provide a passive, redundant, and lower mass option to transfer heat from the fuel to the power conversion system, as opposed to pumped loop designs typically associated with larger FPS. Although many systems have been conceptually designed and a few making it to electrically heated testing, none have been coupled to a real nuclear reactor. A demonstration test named DUFF Demonstration Using Flattop Fission, was planned by the Los Alamos National Lab (LANL) to use an existing criticality experiment named Flattop to provide the nuclearheat source. A team from the NASA Glenn Research Center designed, built, and tested a heatpipe and power conversion system to couple to Flattop with the end goal of making electrical power. This paper will focus on the design and testing performed in preparation for the DUFF test.

In this paper, an integrated solar heatpipe wall space heating system, employing double glazed heatpipe evacuated tube solar collector and forced convective heat transfer condenser, is introduced. Thermal performance of the heatpipe solar collector is studied and a numerical model is developed to investigate thethermal efficiency of the system, the inlet and outlet air temperatures and heatpipe temperature. Furthermore, the system performance is evaluated based on exergy efficiency. In order to verify the precision of the developed model, the numerical results are compared with experimental data. Parametric sensitivity for design features and material associated with the heatpipe, collector cover and insulation is evaluated to provide a combination with higher thermal performance. Simulation results show that applying a solar collector with more than 30 heatpipes is not efficient. The rate of increasing in temperature of air becomes negligible after 30 heatpipes and the trend of the thermal efficiency is descending with increasing heatpipes. The results also indicate that at a cold winter day of January, the proposed system with a 20 heatpipe collector shows maximum energy and exergy efficiency of 56.8% and 7.2%, which can afford warm air up to 30°C. At the end, the capability of the proposed system tomeet the heating demand of a building is investigated. It is concluded that the best method to reach a higher thermal covered area is to apply parallel collectors

Full Text Available Heatpipe is heat transfer device working at a minimum temperature difference of evaporator and condenser. Operating temperature of the heatpipe determine by properties of the working substance and pressure achieved during production. The contribution is focused on the determining the effect of the initial surrounding temperature where the heatpipe is manufactured and on the obtaining performance characteristics produced heatpipes in dependence of manufacturing temperature. Generally hold, that the boiling point of the working liquid decrease with decreasing ambient pressure. Based on this can be suppose that producing of lower ambient temperature during heatpipe manufacturing, will create the lower pressure, the boiling point of the working fluid will lower too and the heatpipe should be better performance characteristics.

Hydrogen and oxygen generation due to the radiolysis of water is a recognized hazard in pipe systems used in the nuclear industry, where the accumulation of hydrogen and oxygen at high points in the pipe system is expected, and explosive conditions exist. Pipe ruptures at nuclear facilities were attributed to hydrogen explosions inside pipelines, in nuclear facilities, i.e., Hamaoka, Nuclear Power Station in Japan, and Brunsbuettel in Germany. Prior to these accidents an ignition source for hydrogen was questionable, but these accidents, demonstrated that a mechanism was, in fact, available to initiate combustion and explosion. Hydrogen explosions may occur simultaneously with water hammer accidents in nuclear facilities, and a theoretical mechanism to relate water hammer to hydrogen deflagrations and explosions is presented herein.

This elemental space radiator heatpipe is designed to operate in the 700 to 875 K temperature range. It consists of a C-C (carbon-carbon) shell made from poly-acrylonitride fibers that are woven in an angle interlock pattern and densified with pitch at high process temperature with integrally woven fins. The fins are 2.5 cm long and 1 mm thick, and provide an extended radiating surface at the colder condenser section of the heatpipe. The weave pattern features a continuous fiber bath from the inner tube surface to the outside edges of the fins to maximize the thermal conductance, and to thus minimize the temperature drop at the condenser end. The heatpipe and radiator element together are less than one-third the mass of conventional heatpipes of the same heat rejection surface area. To prevent the molten potassium working fluid from eroding the C C heatpipe wall, the shell is lined with a thin-walled, metallic tube liner (Nb-1 wt.% Zr), which is an integral part of a hermetic metal subassembly which is furnace-brazed to the inner surface of the C-C tube. The hermetic metal liner subassembly includes end caps and fill tubes fabricated from the same Nb-1Zr alloy. A combination of laser and electron beam methods is used to weld the end caps and fill tubes. A tungsten/inert gas weld seals the fill tubes after cleaning and charging the heatpipes with potassium. The external section of this liner, which was formed by a "Uniscan" rolling process, transitions to a larger wall thickness. This section, which protrudes beyond the C-C shell, constitutes the "evaporator" part of the heatpipe, while the section inside the shell constitutes the condenser of the heatpipe (see figure).

In this study, micro-heatpipe arrays etched into silicon wafers have been investigated for electronic cooling purposes. Micro-heatpipes of triangular cross-section and with liquid arteries were fabricated by wet anisotropic etching with a KOH solution. The microchannels (230 {mu}m wide) are closed by molecular bonding of a plain wafer with the grooved one. A test bench was developed for the micro-heatpipe filling and the thermal characterisation. The temperature profile on the silicon surface is deduced from experimental measurements. The results show that with the artery micro-heatpipe array, filled with methanol, the effective thermal conductivity of the silicon wafer is significantly improved compared to massive silicon. (author)

National Aeronautics and Space Administration — The overall program objective is to develop a high temperature variable conductance heatpipe (VCHP) backup radiator, and integrate it into a Stirling radioisotope...

National Aeronautics and Space Administration — As the need for thermal control technology becomes more demanding Micro-Channel Embedded Pulsating HeatPipes (ME-PHPs) represents a sophisticated and enabling...

Full Text Available Heatpipe with discrete heat transfer property is often called thermal superconductor because it has extremely large thermal conductivity. This special heat transfer property is destroyed by integrating cooling apparatus and further reducing the cooling power of a heatpipe cooler. This paper experimentally studied the heat transfer property of heatpipe influenced by integrated cooling apparatus. To simplify the investigating process, a home-made square heatpipe with the dimensions of L×W×H=10×10×100 mm3 was built with two pieces of copper plates and two pieces of glass plates face to face, respectively. The two pieces of copper plates were constructed with inside walls of capillary structure and the two pieces of glasses were with antifog inside walls for observing the inner phenomenon. Moreover, isothermal circulating cooling water was applied outside the heatpipe instead of cooling fin. The results show that heat vapor in the heatpipe is condensed earlier and cannot reach the remote section of condenser. In other words, the heat transfer property of heatpipe is destroyed by integrating cooling water. This phenomenon causes the unfavorable cooling power of the heatpipe cooler.

The present study focused on how to improve the maximum power output of a thermoelectric generator (TEG) system and move heat to any suitable space using a TEG associated with a loop thermosyphon (loop-type heatpipe). An experimental study was carried out to investigate the power output, the temperature difference of the thermoelectric module (TEM), and the heat transfer performance associated with the characteristic of the researched heatpipe. Currently, internal combustion engines lose more than 35% of their fuel energy as recyclable heat in the exhaust gas, but it is not easy to recycle waste heat using TEGs because of the limited space in vehicles. There are various advantages to use of TEGs over other power sources, such as the absence of moving parts, a long lifetime, and a compact system configuration. The present study presents a novel TEG concept to transfer heat from the heat source to the sink. This technology can transfer waste heat to any location. This simple and novel design for a TEG can be applied to future hybrid cars. The present TEG system with a heatpipe can transfer heat and generate power of around 1.8 V with T TEM = 58°C. The heat transfer performance of a loop-type heatpipe with various working fluids was investigated, with water at high heat flux (90 W) and 0.05% TiO2 nanofluid at low heat flux (30 W to 70 W) showing the best performance in terms of power generation. The heatpipe can transfer the heat to any location where the TEM is installed.

The Passive Cooling System (PCS) driven by natural forces drew research attention since Fukushima nuclear power plant accident. This study investigated the natural convection heat transfer inside of vertical pipe with emphasis on the phenomena regarding the boundary layer interaction. Numerical calculations were carried out using FLUENT 6.3. Experiments were performed for the parts of the cases to explore the accuracy of calculation. Based on the analogy, heat transfer experiment is replaced by mass transfer experiment using sulfuric acid copper sulfate (CuSO{sub 4}. H{sub 2}SO{sub 4}) electroplating system. The natural convection heat transfer inside a vertical pipe is studied experimentally and numerically. Experiments were carried out using sulfuric acid-copper sulfate (H{sub 2}SO{sub 4}-CuSO{sub 4}) based on the analogy concept between heat and mass transfer system. Numerical analysis was carried out using FLUENT 6.3. It is concluded that the boundary layer interaction along the flow passage influences the heat transfer, which is affected by the length, diameter, and Prandtl number. For the large diameter and high Prandtl number cases, where the thermal boundary layers do not interfered along the pipe, the heat transfer agreed with vertical flat plate for laminar and turbulent natural convection correlation within 8%. When the flow becomes steady state, the forced convective flow appears in the bottom of the vertical pipe and natural convection flow appears near the exit. It is different behavior from the flow on the parallel vertical flat plates. Nevertheless, the heat transfer was not different greatly compared with those of vertical plate.

Full Text Available Uniformity of the temperature in the mold plate is of paramount important since it will affect the dimensional stability of the part produced. To provide uniform temperature to the metal plate, many factors need to be considered such as choice of heating technology, uniformity of a heat source, a type of control, etc. This paper aims to study the temperature uniformity of metal plate using closed-loop oscillating heatpipe (CLOHP as a heat transfer device. The metal plates which were P-20 with the size of 306 x 130 mm2 were used. Metal plate was gouged to a depth of 3 mm for installing the CLOHP. Distances from the heating device to the metal plate surface were 5 and 10 mm. The surface temperatures of the metal plate were controlled at 80, 90, 100, 110, 120, and 130°C. Sixteen pointa of temperature were recorded. The results were then compared to those using the heat source as the cartridge heater arranged in the similar way with the same heating capacity. Once the system entered the steady state, it was found that the temperature distribution of metal plate using the CLOHP has a deviation in the range of ± 1.00°C and ± 0.94°C at the CLOHP depth of 5 mm. and 10 mm., respectively. While those of using cartridge heater deviated in the range of ± 1.35°C and ± 1.16°C. Compare to the recommended value from the ASTM Standard that the mold surface temperature need to be in the range of ± 2.0°C, the CLOHP shows the very promising results.

Interim results of an ongoing program to assist the U.S. Nuclear Regulatory Commission (NRC) in developing regulatory positions on the seismic analyses of piping and overall safety margins of piping systems are reported. Results of: (1) reviews of seismic testing of piping components performed as part of the Electric Power Research Institute (EPRI)/NRC Piping and Fitting Dynamic Reliability (PFDR) Program, and (2) assessments of safety margins inherent in the ASME Code, Section III, piping seismic design criteria as revised by the 1994 Addenda are reported. The reviews indicate that the margins inherent in the revised criteria may be less than acceptable and that modifications to these criteria may be required.

Experimental evidence shows the importance of external boundary conditions on the overall performance of a rotating heatpipe condenser. Data are presented for the boundary conditions of constant heat flux and constant wall temperature for rotating heatpipes containing either pure vapor or a mixture of vapor and noncondensable gas as working fluid.

Full Text Available In electrical and electronic industry due to miniaturization of electronic components heat density increases which, in turns increases the heat flux inside it. Scientist and many researchers are doing lot of work in this field for thermal management of devices. Heatpipe is a device that is used in electronic circuit (micro and power electronics, spacecraft & electrical components for cooling purpose. It is based on the principle of evaporation and condensation of working fluid. Heatpipe made up of three main parts are evaporator, adiabatic and condenser sections. In this working fluid vaporise at evaporator and transfers heat to condenser by adiabatic section where heat release to surrounding. Vapour flows possible from evaporator to condenser section due to vapour pressure difference exist between them. Use of heatpipe material, type of working fluid & its property, wick structure, orientation, filled ratio, operating condition, dimensions of pipe has a prominent effect on heatpipe performance. Variation of these parameters for minimum thermal resistance gives better performance.

Flat heatpipes have various technical applications, one of the most important being the cooling of electronic components[9]. Their continuous development is due to the fact that these devices permit heat transfer without external energetic contribution. The practical exploitation of flat heatpipes however is limited by the fact that dissipated power can only reach a few hundred watts. The present paper aims to advance a new method for the intensification of convective heat transfer. A centrifugal mini impeller, driven by a turntable which incorporates four permanent magnets was designed. These magnets are put in motion by another rotor, which in its turn includes two permanent magnets and is driven by a mini electrical motor. Rotation of the centrifugal blades generates speed and pressure increase of the cooling agent brought to vapor state within the flat micro heatpipe. It's well known that the liquid suffers biphasic transformations during heat transfer inside the heatpipe. Over the hotspot (the heat source being the electronic component) generated at one end of the heatpipe, convective heat transfer occurs, leading to sudden vaporization of the liquid. Pressures generated by newly formed vapors push them towards the opposite end of the flat heatpipe, where a finned mini heat sink is usually placed. The mini-heat exchanger is air-cooled, thus creating a cold spot, where vapors condensate. The proposed method contributes to vapor flow intensification by increasing their transport speed and thus leading to more intense cooling of the heatpipe.

Alkali metal heat-pipe receivers have been identified as a desirable interface to couple a Stirling-cycle engine with a parabolic dish solar concentrator. The reflux receiver provides power nearly isothermally to the engine heater heads while de-coupling the heater head design from the solar absorber surface design. The independent design of the receiver and engine heater head leads to high system efficiency. Heatpipe reflux receivers have been demonstrated at approximately 30 kW{sub t} power throughput by others. This size is suitable fm engine output powers up to 10 kW{sub e}. Several 25-kW{sub e}, Stirling-cycle engines exist, as well as designs for 75-kW{sub t} parabolic dish solar concentrators. The extension of heatpipe technology from 30 kW{sub t} to 75 kW{sub t} is not trivial. Heatpipe designs are pushed to their limits, and it is critical to understand the flux profiles expected from the dish, and the local performance of the wick structure. Sandia has developed instrumentation to monitor and control the operation of heatpipe reflux receivers to test their throughput limits, and analytical models to evaluate receiver designs. In the past 1.5 years, several heatpipe receivers have been tested on Sandia`s test bed concentrators (TBC`s) and 60-kW{sub t} solar furnace. A screen-wick heatpipe developed by Dynatherm was tested to 27.5 kW{sub t} throughput. A Cummins Power Generation (CPG)/Thermacore 30-kW{sub t} heatpipe was pushed to a throughput of 41 kW{sub t} to verify design models. A Sandia-design screen-wick and artery 75-kW{sub t} heatpipe and a CPG/Thermacore 75-kW{sub t} sintered-wick heatpipe were also limit tested on the TBC. This report reviews the design of these receivers, and compares test results with model predictions.

A novel loop heatpipe(LHP)cooling device for high power LED is developed.The thermal capabilities, including startup performance,temperature uniformity and thermal resistance of the loop heatpipe under different heat loads and incline angles have been investigated experimentally.The obtained results indicate that the thermal resistance of the heatpipeheat sink is in the range of 0.19―3.1 K/W,the temperature uniformity in the evaporator is controlled within 1.5℃,and the junction temperature of high power LED can be controlled steadily under 100℃for a heat load of 100 W.

Currently, large amounts of thermal energy dissipated from automobiles are emitted through hot exhaust pipes. This has resulted in the need for a new efficient recycling method to recover energy from waste hot exhaust gas. The present experimental study investigated how to improve the power output of a thermoelectric generator (TEG) system assisted by a wickless loop heatpipe (loop thermosyphon) under the limited space of the exhaust gas pipeline. The present study shows a novel loop-type heatpipe-assisted TEG concept to be applied to hybrid vehicles. The operating temperature of a TEG's hot side surface should be as high as possible to maximize the Seebeck effect. The present study shows a novel TEG concept of transferring heat from the source to the sink. This technology can transfer waste heat to any local place with a loop-type heatpipe. The present TEG system with a heatpipe can transfer heat and generate an electromotive force power of around 1.3 V in the case of 170°C hot exhaust gas. Two thermoelectric modules (TEMs) for a conductive block model and four Bi2Te3 TEMs with a heatpipe-assisted model were installed in the condenser section. Heat flows to the condenser section from the evaporator section connected to the exhaust pipe. This novel TEG system with a heatpipe can be placed in any location on an automobile.

The objective of this project was the conceptual design of a Central Solar Receiver Gas Turbine Plant which utilizes a high temperature heatpipe receiver. Technical and economic feasibility of such a plant was to be determined and preliminary overall cost estimates obtained. The second objective was the development of the necessary heatpipe technology to meet the requirements of this receiver. A heatpipe receiver is ideally suited for heating gases to high temperatures. The heatpipes are essentially loss free thermal diffusers which accept a high solar flux and transform it to a lower flux which is compatible with heat transferred to gases. The high flux capability reduces receiver heating surface, thereby reducing receiver heat losses. An open recuperative air cycle with a turbine inlet temperature of 816/sup 0/C (1500/sup 0/F) was chosen as the baseline design. This results in peak metal temperatures of about 870/sup 0/C (1600/sup 0/F). The receiver consists of nine modular panels which form the semicircular backwall of a cavity. Gas enters the panels at the bottom and exits from the top. Each panel carries 637 liquid metal heatpipes which are mounted at right angle to the gas flow. The evaporators of the heatpipes protrude from the flux absorbing front surface of the panels, and the finned condensors traverse the gas stream. Capital cost estimates were made for a 10 MW(e) pilot plant. The total projected costs, in mid-1978 dollars, range from $1,947 to $2,002 per electrical kilowatt. On the same basis, the cost of a water/steam solar plant is approximately 50% higher.

Future space missions will require thermal transport devices with the ability to handle transient pulse heat loads. A novel design of a high-temperature axially grooved heatpipe (HP) which incorporates thermal energy storage (TES) to migrate pulse heat loads was presented. A phase-change material (PCM) which is encapsulated in cylindrical containers was used for the thermal energy storage. The transient response of the HP/TES system under two different types of pulse heat loads was studied analytically. The first type is pulse heat loads applied at the heatpipe evaporator, the second type is reversed-pulse heat loads applied at the condenser. In this research, a new three-dimensional alternating-direction-implicit (ADI) method was developed to model the heat conduction through the heatpipe wall and wicks, including the liquid flow in grooves. A very important characteristic of this new ADI method is that it is consistent with physical considerations. Compared with the well-known Brian's and Douglas's ADI methods, this new ADI method had higher accuracy and requires less computer storage. In the numerical solution of heat transfer problems with phase change (Stefan-type problem), a modified Pham's method which includes features from enthalpy and heat capacity methods was used to simulate the melting and solidification processes of the PCG. The vapor flow was assumed quasi-steady and one-dimensional, and was coupled with the evaporation and condensation on the heatpipe inside wall surface and the surfaces of the PCM containers. The transient responses of three different HP/TES configurations were compared: (1) a heatpipe with a large empty cylinder installed in the vapor core, (2) a heatpipe with a large PCM cylinder, and (3) a heatpipe with six small PCM cylinders. From the numerical results, it was found that the PCM is very effective in mitigrating the adverse effect of pulse heat loads. The six small PCM cylinders are more efficient than the large PCM

The design of a solar operated intermittent-duty aqua-ammonia type of absorption refrigerator is described. The generator is heated by an integral acetone heatpipe, the evaporator of which is in the form of a low-thermal-mass flat plate collector. The condenser is air cooled. The absorber is likewise cooled via a second R22 heat-pipe system by convection/radiation panels. Initial test results for the collector-generator loop are reported for a single-glazed collector. A discussion of overall performance is presented.

In the present work, different operation modes of a latent heat thermal energy storage system assisted by a heatpipe network were studied experimentally. Rubitherm RT55 enclosed by a vertical cylindrical container was used as the Phase Change Material (PCM). The embedded heatpipe network consisting of a primary heatpipe and an array of four secondary heatpipes were employed to transfer heat to the PCM. The primary heatpipe transports heat from the heat source to the heat sink. The secondary heatpipes transfer the extra heat from the heat source to PCM during charging process or retrieve thermal energy from PCM during discharging process. The effects of heat transfer fluid (HTF) flow rate and temperature on the thermal performance of the system were investigated for both charging and discharging processes. It was found that the HTF flow rate has a significant effect on the total charging time of the system. Increasing the HTF flow rate results in a remarkable increase in the system input thermal power. The results also showed that the discharging process is hardly affected by the HTF flow rate but HTF temperature plays an important role in both charging and discharging processes. The authors would like to acknowledge the financial supports by Temple University for the project.

Designing thermal control systems for electronic products has become very challenging due to the continuous miniaturization and increasing performance demands. Two-phase cooling solutions, such as heatpipes or vapor chambers, are increasingly used as they offer higher thermal coefficients for heat

The capillary pump loop (CPL) was re-introduced as a potential candidate for the management of large heat loads. It is currently being evaluated for application in the thermal management of large space structures. Test efforts were conducted to establish the feasibility of the CPL heatpipe design.

The principal objective of this Phase 2 SBIR program was to develop and demonstrate a practically insoluble coating for nickel-based superalloys for Stirling engine heatpipe applications. Specific technical objectives of the program were: (1) Determine the solubility corrosion rates for Nickel 200, Inconel 718, and Udimet 72OLI in a simulated Stirling engine heatpipe environment, (2) Develop coating processes and techniques for capillary groove and screen wick structures, (3) Evaluate the durability and solubility corrosion rates for capillary groove and screen wick structures coated with an insoluble coating in cylindrical heatpipes operating under Stirling engine conditions, and (4) Design and fabricate a coated full-scale, partial segment of the current Stirling engine heatpipe for the Stirling Space Power Convertor program. The work effort successfully demonstrated a two-step nickel aluminide coating process for groove wick structures and interior wall surfaces in contact with liquid metals; demonstrated a one-step nickel aluminide coating process for nickel screen wick structures; and developed and demonstrated a two-step aluminum-to-nickel aluminide coating process for nickel screen wick structures. In addition, the full-scale, partial segment was fabricated and the interior surfaces and wick structures were coated. The heatpipe was charged with sodium, processed, and scheduled to be life tested for up to ten years as a Phase 3 effort.

Radiative heat transfer is usually of substantial importance in cryogenics when systems are designed and thermal budgeting is carried out. However, the contribution of pipes is commonly assumed to be comparably low since the warm and cold ends as well as their cross section are fairly small. Nevertheless, for a first assessment of each pipe rough estimates are always appreciated. In order to estimate the radiative heat transfer with traditional “paper and pencil“ methods there is only one analytical case available in literature - the case of plane-parallel plates. This case can only be used to calculate the theoretical lower and the upper asymptotic values of the radiative heat transfer, since pipe wall radiation properties are not taken into account. For this paper we investigated the radiative heat transfer estimation in pipes with various wall emissivities with the help of numerical simulations. Out of a number of calculation series we could gain an empirical extension for the used approach of plane-parallel plates. The model equation can be used to carry out enhanced paper and pencil estimations for the radiative heat transfer through pipes without demanding numerical simulations.

Loop heatpipes (LHPs) are hermetic heat-transfer devices operating on a closed evaporation-condensation cycle with the use of capillary pressure for pumping the working fluid [1]. In accordance with this, they possess all the main advantages of conventional heatpipes, but, as distinct from the latter, have a considerably higher heat-transfer capacity, especially when operating in the ''antigravity'' regime, when heat is transferred from above downwards. Besides, LHPs possess a higher functional versatility, are adaptable to different operating conditions and provide great scope for various design embodiments. This is achieved at the expense of both the original design of the device and the properties of the wick - a special capillary structure used for the creation of capillary pressure. The LHP schematic diagram is given in Fig. 1. The device contains an evaporator and a condenser - heat exchanger connected by means of smooth-walled pipe-lines with a relatively small diameter intended for separate motion of vapor and liquid. At present loop heatpipes are most extensively employed in thermoregulation systems of spacecrafts. Miniature LHPs are used for cooling electronics and computers. At the same time there exists a considerable potential of using these devices for the recovery of low-grade (waste) heat from different sources, and also in systems of sun heat supply. In the latter case LHPs may serve as an efficient heat-transfer link between a sun collector and a heat accumulator, which has a low thermal resistance and does not consume any additional energy for pumping the working fluid between them. (orig.)

Full Text Available The heat recovery by the heatpipeheat exchangers was studied in the tropics. Heatpipeheat exchangers with two, four, six, and eight numbers of rows were examined for this purpose. The coil face velocity was set at 2 m/s and the temperature of return air was kept at 24°C in this study. The performance of the heatpipeheat exchangers was recorded during the one week of operation (168 hours to examine the performance data. Then, the collected data from the one week of operation were used to estimate the amount of energy recovered by the heatpipeheat exchangers annually. The effect of the inside design temperature and the coil face velocity on the energy recovery for a typical heatpipeheat exchanger was also investigated. In addition, heatpipeheat exchangers were simulated based on the effectiveness-NTU method, and their theoretical values for the thermal performance were compared with the experimental results.

Three nuclear reactor space power system designs are described that demonstrate how the use of high temperature heatpipes for reactor heat transport, combined with direct conversion of heat to electricity, can result in eliminating pumped heat transport loops for both primary reactor cooling and heat rejection. The result is a significant reduction in system complexity that leads to very low mass systems with high reliability, especially in the power range of 1 to 20 kWe. In addition to removing heat exchangers, electromagnetic pumps, and coolant expansion chambers, the heatpipe/direct conversion combination provides such capabilities as startup from the frozen state, automatic rejection of reactor decay heat in the event of emergency or accidental reactor shutdown, and the elimination of single point failures in the reactor cooling system. The power system designs described include a thermoelectric system that can produce 1 to 2 kWe, a bimodal modification of this system to increase its power level to 5 kWe and incorporate high temperature hydrogen propulsion capability, and a moderated thermionic reactor concept with 5 to 20 kWe power output that is based on beryllium modules that thermally couple cylindrical thermionic fuel elements (TFEs) to radiator heatpipes.

Three nuclear reactor space power system designs are described that demonstrate how the use of high temperature heatpipes for reactor heat transport, combined with direct conversion of heat to electricity, can result in eliminating pumped heat transport loops for both primary reactor cooling and heat rejection. The result is a significant reduction in system complexity that leads to very low mass systems with high reliability, especially in the power range of 1 to 20 kWe. In addition to removing heat exchangers, electromagnetic pumps, and coolant expansion chambers, the heatpipe/direct conversion combination provides such capabilities as startup from the frozen state, automatic rejection of reactor decay heat in the event of emergency or accidental reactor shutdown, and the elimination of single point failures in the reactor cooling system. The power system designs described include a thermoelectric system that can produce 1 to 2 kWe, a bimodal modification of this system to increase its power level to 5 kWe and incorporate high temperature hydrogen propulsion capability, and a moderated thermionic reactor concept with 5 to 20 kWe power output that is based on beryllium modules that thermally couple cylindrical thermionic fuel elements (TFE's) to radiator heatpipes.

Full Text Available The main purpose of this article is to analyze the selecting of technological parameters for the heat exchanger to improve the heat transfer and reduce the noise during operation in the heatingpipe, which is used in the different systems of the planes and helicopters. In result of this study, the best technical parameters are found, considering different variations of deformation cutting heat exchanger pipes.

Full Text Available Heatpipes have been used extensively in the electronic industry for decades especially in laptop computers. For cost-effectiveness, a single heatpipe is designed to simultaneously transfer heat from both the Central Processing Unit (CPU and the Graphics Processing Unit (GPU inside the main board to the heat sink. This causes the efficiency of the heatpipe to change without any theoretical prediction. In this research, thermal performance of a sintered-wick heatpipe with double heat sources has been experimentally and numerically investigated by utilizing the Finite Element Method (FEM. The focus being the effect that the distance between the two heat sources and also the power input pattern (heat source#1 (HT1: heat source#2(HT2 has on temperature and thermal resistance of the heatpipe. The first heat source (HT1 was located at one end and the heat sink was located at another end of the heatpipe, while another heat source (HT2 was placed between HT1 and a heat sink. The ratios of heat input power were controlled at 10W:10W, 20W:10W and 30W:10W. Two copper blocks (15 mmÃ15 mm were used as heat sources for the evaporator section (Le1, Le2 to electrically supply heat to the bottom half of the heatpipe. A mathematical model using the Finite Element Method (FEM was established to calculate temperature and thermal resistance. The speed of the cooling fan was adjusted to maintain constant operating temperature at the adiabatic section throughout the tests. The operating temperature was controlled at 60 Â± 3Â°C. It was noted that, when distance between the heat sources was increased from 0 mm to 75 mm, thermal resistance slightly decreased from 0.589-0.53Â°C/W respectively. Heat source 2, therefore, should be placed as close as possible to the condenser section. Both heat sources should have a distance between them of at least 12 mm, which minimizes heat accumulation. When the power input of HT1 was increased from 10 W to 30W (HT2 was

Full Text Available Heat-balance thermal protection is non-ablating thermal protection for leading edge of hypersonic vehicle. Heat will be quickly transferred from high aerodynamic heating area to low aerodynamic heating area, where the energy will be released by radiation. The temperature of high aerodynamic heating area could be reduced to protect the designed structure from being burned down. Heat-balance thermal protection is summarized. The research on heat-pipe for heat-balance thermal protection is introduced.

Heat-balance thermal protection is non-ablating thermal protection for leading edge of hypersonic vehicle. Heat will be quickly transferred from high aerodynamic heating area to low aerodynamic heating area, where the energy will be released by radiation. The temperature of high aerodynamic heating area could be reduced to protect the designed structure from being burned down. Heat-balance thermal protection is summarized. The research on heat-pipe for heat-balance thermal protection is intro...

Full Text Available A numerical method is proposed to determine the heat transfer capability of the high-temperature heatpipe and the stagnation temperature with supersonic vehicle leading edge applications. The finite element method is employed here to perform the temperature field simulation. Without considering the heat transfer limitations of the heatpipe, such as capillary limit and sonic limit, both numerical and experimental results indicate that equivalent high thermal conductivity method is a reasonable way to simulate the heat transfer capability of the high-temperature heatpipe in preliminary design of a heat-pipe-cooled leading edge. Several important parameters’ effects on the thermal protection performance are also numerically investigated.

Most of previous elastic-plastic fracture studies for LBB assessment of low alloy steel piping have been focused on base metals and weld metals. In contract, the heat affected zone of welded pipe has not been studied in detail primarily because the size of heat affected zone in welded pipe os too small to make specimens for mechanical properties measurement. When structural members are joined by welding, the base metal is heated to its melting point and then cooled rapidly. As a result of this very severe thermal cycle, mechanical properties in the heat affected zone can be degraded by grain coarsening, the precipitation and the segregation of trace impurities. In this study, a thermal and microstructural analysis is performed, and mechanical properties are measured for the weld heat affected zone of SA106Gr.C low allowed piping steel. In addition, inter critical annealing treatment. in two-phase (alpha+gamma) region was performed to investigate the possibilities of improving the toughness and reducing dynamic strain aging (DSA) susceptibility for giving allowable LBB safety margins. From the results, intercritical annealing is shown to give a smaller ductility loss due to DSA than the case of as-received material. Furthermore, the intercritical annealing was able to increase the impact toughness by a factor of 1.5 compared to the as-received material.

The enhancement of axial heat and mass transfer by laminar flow oscillation in pipes with axial gradients in temperature and concentration has been studied analytically for the cases of insulated and conducting walls. The axial diffusivity can exceed its molecular counterpart by many orders of magnitude, with a quadratic scaling on the pressure-gradient amplitude and the Prandtl or Schmidt number, and is a bimodal function of oscillatory frequency: quasi-steady behavior at low frequencies and a power-law decay at high frequencies. When the pipe wall is conductive and of sufficient thickness, and the flow oscillation is quasi-steady, the axial diffusivity may be enhanced by a further factor of about ten as a result of increased radial diffusion, for liquid and gas flows in pipes with walls with a wide range of thermal conductivities. Criteria for the wall thickness required to achieve this additional enhancement and for the limits placed on the validity of these solutions by viscous dissipation are also deduced. When the heat transfer per unit flow work achieved by oscillatory pipe flow is contrasted with that of a conventional parallel-flow heat exchanger, it is found to be of comparable size and the ratio of the two is shown to be a function only of the pipe geometry, heat-exchanger mean velocity, and fluid viscosity.

Full Text Available Achievements of the E.O. Paton Electric Welding Institute in development of domestic samples of equipment with elements of adaptive control for automatic position pipe welding during assembly and repair of power units of nuclear and heat power electric stations, in shipbuilding and chemical engineering, at enterprises of oil-and-gas complex and in other branches of industry are presented.

Integral heatpipe sandwich panels, which synergistically combine the thermal efficiency of heatpipes and the structural efficiency of honeycomb sandwich construction, were conceived as a means of alleviating thermal stress problems in the Langley Scramjet Engine. Test panels which utilized two different wickable honeycomb cores, facesheets with screen mesh sintered to the internal surfaces, and a liquid metal working fluid (either sodium or potassium) were tested by radiant heating at various heat load levels. The heatpipe panels reduced maximum temperature differences by 31 percent with sodium working fluid and 45 percent with potassium working fluid. Results indicate that a heatpipe sandwich panel is a potential, simple solution to the engine thermal stress problem. Other interesting applications of the concept include: cold plates for electronic component and circuit card cooling, radiators for large space platforms, low distortion large area structures (e.g., space antennas) and laser mirrors.

The research presented in this paper aimed to determine the maximum heat transfer a heatpipe can achieve. To that purpose the structure of the capillary layer which can be deposited on the walls of the heatpipe was investigated. For the analysis of different materials that can produce capillarity, the present study takes into account the optimal thickness needed for this layer so that the accumulated fluid volume determines a maximum heat transfer. Two materials that could be used to create a capillary layer for the heatpipes, were investigated, one formed by sintered copper granules (the same material by which the heatpipe is formed) and a synthetic material (cellulose sponge) which has high absorbing proprieties. In order to experimentally measure and visualize the surface characteristics for the considered capillary layers, laser profilometry was employed.

During severe accident of a light water reactor (LWR), reactor coolant piping would be damaged when the piping is subjected to high internal pressure and very high temperature due to heat transfer from high-temperature gas and decay heat from wall-deposited fission product (FP), both from degraded core. In such a case, high-temperature fast creep deformation could be the main cause for the pipe failure. For the evaluation of piping integrity during severe accidents, a method to predict such high-temperature fast creep deformation should be developed, using a creep constitutive equation considering tertiary creep behavior which has not been considered well in the pipe failure analyses. In this study, a creep constitutive equation was developed first based on the Kachanov-Ravotnov isotropic damage rule that considers the tertiary creep behavior. JAERI creep tensile test data for both nuclear-grade cold-drawn SUS316N and hot-extruded SUS316 materials were used to determine coefficients of the developed constitutive equation. Using the developed constitutive equation, finite element analyses were performed for local creep deformation of coolant piping under two temperature conditions: uniform temperature and temperature gradient. The analytical results indicated the damage variable being integrated following the evolution of creep damage can indicate pipe wall internal damage condition quantitatively. The damage variable was confirmed further to be able to reproduce the observation in JAERI piping failure tests, that is, pipe failure from the wall outside. (author)

The HeatPipe Stirling Engine (HP-1000), a free-piston Stirling engine incorporating three heat exchanger modules, each having a sodium filled heatpipe, has been tested at the NASA-Lewis Research Center as part of the Civil Space Technology Initiative (CSTI). The heat exchanger modules were designed to reduce the number of potential flow leak paths in the heat exchanger assembly and incorporate a heatpipe as the link between the heat source and the engine. An existing RE-1000 free-piston Stirling engine was modified to operate using the heat exchanger modules. This paper describes heat exchanger module and engine performance during baseline testing. Condenser temperature profiles, brake power, and efficiency are presented and discussed.

A new method of laying of district heatingpipes is described with its advantages and disadvantages. The method has earlier been applied to installation of gas pipes and broadband, but has to our knowledge never been used in connection to district heating. The method aims at shortening the laying time and minimising the impact on the asphalt layer, thus reducing the laying costs. The idea is to cold install the pipes into a milled, narrow and shallow trench that is refilled with foam concrete. Environmental impacts caused by the new laying method are studied in comparison with the traditional laying method. Emissions of carbon dioxide, nitrogen oxides and sulphur dioxide to air from activities differing between the two laying methods during construction of DN40 twin pipe networks are considered as well as emissions related to distribution heat losses from the networks. There is no environmental objective against using the new method considering the studied emissions. Laying according to the new and the traditional method cause emissions of the same order of magnitude. Calculated temperature of the casing does not indicate any problem with accelerated thermal oxidation of the casing pipe due to laying in the thermally insulating foam concrete. (orig.)

This paper presents a novel ultrasonic guided wave based inspection methodology for detecting and evaluating gas accumulation in nuclear cooling pipe system. The sensing is in-situ by means of low-profile permanently installed piezoelectric wafer sensors to excite interrogating guided waves and to receive the propagating waves in the pipe structure. Detection and evaluation is established through advanced cross time-frequency analysis to extract the phase change in the sensed signal when the gas is accumulating. A correlation between the phase change and the gas amount has been established to provide regulatory prediction capability based on measured sensory data.

An experimental study of the dynamics of heatpipes with steel wool and metal fiber wicks, in particular of startup and transition from one operating mode to another, is presented. The dynamics effect of the initial heat flux in the evaporator when NaK is the working fluid is determined. The effect of interaction between the liquid and vapor phases on the heat and mass transfer from the vapor condensing on the pipe wall is analyzed.

The present numerical study aims to evaluate the heating and cooling potential of buried pipes in three cities of South Brazil i.e. Curitiba, Florianopolis and Porto-Alegre. In a first part, ground temperatures at the buried pipe location (between 1 and 3 m depth) are calculated by both a simplified model and a three-dimensional volume-finite code (SOLUM). Then, a prototypical house and its buried pipe are modeled with a building energy simulation tool (TRNSYS) to evaluate the positive and negative effects of such system on thermal comfort and heating and cooling energy. Results show that this passive system is particularly efficient in Curitiba, can reduce energy consumption in Porto Alegre and is not well-adapted to Florianopolis. (author)

Full Text Available This study focused on investigating the influence of longitudinal vibrations, the condensation section temperature, and the inclination angles on the heat transfer performance of grooved cylindrical copper heatpipes with lengths of 600 and 150 mm and an outer diameter of 8 mm. The inclination angles of the tested heatpipes were 0°, ±45°, and ±90°. Longitudinal vibrations with frequencies of 3, 4, 5, 6, and 9 Hz and amplitudes of 2.8, 5, 10, 15, 20, and 25 mm, which resulted in accelerations between 0.1 and 1.01 g, were experimentally tested. The condensation section temperatures were set at 20°C, 30°C, and 40°C. A heating jacket and a cooling sleeve were installed at the evaporation and condensation sections of the test cell to simulate a constant heat flux and a constant temperature boundary, respectively. The results showed that with the heatpipe placed with the condensation section on top and the evaporation section on bottom, a fairly low and constant thermal resistance (approximately 0.25 K/W for the 600-mm heatpipe and 0.75–1.2 K/W for the 150-mm heatpipe was obtained, both with and without heatpipe vibration and regardless of the condensation section temperature.

In the frame of the BRITE-EURAM european programme (KHIEPCOOL project), a literature survey on the main beat pipe and micro heatpipe technologies developed for thermal control of electronic equipment has been carried out. The conventional heatpipes are cylindrical, flat or bellow tubes, using wicks or axial grooves as capillary structures. In the field of micro heatpipes, the component interconnection substrate. The best performances were achieved with Plesch`s axially grooved flat miniature heatpipe, which is able to transfer a heat flux of about 60 W.cm{sup -2}. Theoretical models have shown that the performance of micro heatpipe arrays increase with increasing tube diameter, decreasing tube length and increasing heatpipe density. The heatpipe technologies are classified and compared according to their geometry and location in the system. A list of about 150 references, classified according to their subjects, is presented. (authors) 160 refs.

Previous studies have shown that the investment costs for district heating installations in suburban areas can be lowered with more rational construction work. This project has studied the possibilities of decreasing the laying depth for pipes in residential-area roads without risking damage on neither pipe nor road surface. An inventory of regulations from national and local authorities and district heating companies in Sweden was done. The larger cities have specific requirements regarding laying depth in road structures. In most places, however, the guidelines issued by the Swedish District Heating Association are followed. And in smaller cities, the question is handled directly by the municipal district heating company. In some places, e.g., Goeteborg, Joenkoeping and Luleaa, the local authorities and the district heating company have agreed on a smaller laying depth under certain circumstances. An analysis of the costs related to the excavation work, backfilling and asphalt laying showed that the costs can be reduced with about 30 % by decreasing the laying depth from 600 mm to 350 mm. A field trial was done with four twin pipes of dimension 2 x DN 32/160 laid 600 mm, 380 mm, 280 mm and 180 mm below the asphalt surface in a road with heavy traffic. Apart from the laying depth, the installation work was done in accordance with the guidelines from the Swedish District Heating Association. During traffic loading, measurements of internal deformations of the pipes, wheel-track depths in the asphalt surface and load-bearing capacity of the road structure were made. The deformation of the pipes is negligible at all laying depths. This is likely due to an arching action from the backfill which supports most of the forces from the traffic load. Significant wheel-tracks were measured, but they seem to correspond directly to settlements in the new soil. Hence, a shallower pipe trench leads to less prominent wheel-tracks. Shallow pipe burial yields slightly larger heat

Full Text Available High heat flux is the major reason for the malfunctioning or shortened life of high-power light-emitting diodes (LEDs or integrated circuit (IC components. Cooling technical devices have been widely studied in recent years. A heatpipe made of silicon wafer and Pyrex 7740 has been used in the experiments. Silicon-to-Pyrex bonding is used for the visualization of the flow behavior of the working liquid in heat transfer. A thermal behavior testing system for micro heatpipes (MHPs, including a vacuum chamber, heat flux sensors and thermocouples, was designed and established. The experiments revealed the characteristics of the MEMS heatpipe in LEDs heat transfer, and the maximum equivalent thermal conductivity of the MHPs was 10.6 times that of the silicon wafer. Furthermore, the structure of MHP can be optimized based on these experimental results. They can also be the experimental basis for theoretical study of two-phase flow on the micro scale.

Dryout induced by vapor throttling makes control of equipment temperature less dependent on variations in sink environment. Mechanism controls flow of vapor in heatpipe by using valve in return path to build difference in pressure and also difference in saturation temperature of the vapor. In steady state, valve closes just enough to produce partial dryout that achieves required temperature drop.

We present a new, low-cost method of building an all copper heat-pipe oven that increases the practicality of this device in advanced undergraduate instructional labs. The construction parts are available at local hardware and plumbing supply stores, and the assembly techniques employed are simple and require no machining. (Contains 1 footnote, 3…

The pulsating heatpipe (PHP) has been increasingly studied in cryogenic application, for its high transfer coefficient and quick response. Compared with Nb3Sn and NbTi, MgB2 whose critical transformation temperature is 39 K, is expected to replace some high-temperature superconducting materials at 25 K. In order to cool MgB2, this paper designs a Hydrogen Pulsating HeatPipe, which allows a study of applied heat, filling ratio, turn number, inclination angle and length of adiabatic section on the thermal performance of the PHP. The thermal performance of the hydrogen PHP is investigated for filling ratios of 35%, 51%, 70% at different heat inputs, and provides information regarding the starting process is received at three filling ratios.

We describe the development of a new technology for cooling microelectronics. This report documents the design, fabrication, and prototype testing of micro scale heatpipes embedded in a flat plate substrate or heat spreader. A thermal model tuned to the test results enables us to describe heat transfer in the prototype, as well as evaluate the use of this technology in other applications. The substrate walls are Kovar alloy, which has a coefficient of thermal expansion close to that of microelectronic die. The prototype designs integrating micro heatpipes with Kovar enhance thermal conductivity by more than a factor of two over that of Kovar alone, thus improving the cooling of micro-electronic die.

Above-boiling temperature conditions, as encountered, for example, in geothermal reservoirs and in geologic repositories for the storage of heat-producing nuclear wastes, may give rise to strongly altered liquid and gas flow processes in porous subsurface environments. The magnitude of such flow perturbation is extremely hard to measure in the field. We therefore propose a simple temperature-profile method that uses high-resolution temperature data for deriving such information. The energy that is transmitted with the vapor and water flow creates a nearly isothermal zone maintained at about the boiling temperature, referred to as a heatpipe. Characteristic features of measured temperature profiles, such as the differences in the gradients inside and outside of the heatpipe regions, are used to derive the approximate magnitude of the liquid and gas fluxes in the subsurface, for both steady-state and transient conditions.

The thermal micro pipes which were aimed to the cooling of the electrical systems, were realized until the present day in different constructive ways. If the first thermal pipes had had at the base the thermo-siphon system [1], afterwards it had been developed the thermal micro pipes [2], thanks to their increased capacity of heat dissipation of the surfaces covered by big densities of the thermal flow. The article, presents in the first part, the physical characteristics of the elements which embody a thermal micro pipe and which generates an excess of liquid. For this it has been realized an experimental setup. Measurements were taken by aid of a laser profilometer of the coverage material in two cases. The first one considered the material without being soaked in the liquid, and for the second one, the measurements were taken when the material was supersaturated with liquid. Since the setup allows for temperature monitoring, determinations were effectuated in the vaporization, adiabatic and condensation areas. The temperature field was determined along a thermal micro pipe in the case of extra fluid. The experimental determinations allowed verifying if the method proposed by Mihai and Olariu [3], for cooling of the electronic components, through a semi active method with the share of extra fluid in the vaporization area of the thermal micro pipe, works. It was studied how the temperature modifies in the vaporization and condensation areas and by the contrast of the theoretical results obtained through the evaluation with the experimental ones.

A split-system solar cooker is described which has its flat-plate collector outdoors and the cooking chamber inside the kitchen, with heatpipes transferring the energy between the two. Test results are discussed, and areas of possible improvement are indicated. The results of a series of tests conducted to ascertain the most suitable heat transfer arrangement in the cooking chamber are presented. Recommendations are made for further areas of improvement.

Full Text Available A large number of variables is the main problem of designing systems which uses heatpipes, whether it is a traditional - gravity, or advanced - capillary, pulsating, advanced heatpipes. This article is a methodology for measuring the thickness of the falling condensate in gravitational heatpipes, with using the optical triangulation method, and the evaluation of risks associated with this method.

A large number of variables is the main problem of designing systems which uses heatpipes, whether it is a traditional - gravity, or advanced - capillary, pulsating, advanced heatpipes. This article is a methodology for measuring the thickness of the falling condensate in gravitational heatpipes, with using the optical triangulation method, and the evaluation of risks associated with this method.

Full Text Available This study presents a design method to fabricate a novel hybrid-structure flat plate heatpipe (NHSP heatpipe for a concentrator photovoltaic. The NHSP heatpipe is composed of a flattened copper pipe and a sintered wick structure, and a coronary-stent-like rhombic copper mesh supports the structure. The coronary-stent-like supporting structure enhances the mechanical strength and shortens the reflux path of the working fluid. Experiments demonstrate that the sintered capillary heatpipe reduces the thermal resistance by approximately 72%, compared to a traditional copper mesh-screen heatpipe. Furthermore, it can reduce thermal resistance by 65% after a supporting structure is added to the heatpipe. The results show that the NHSP heatpipe provided the best performance for the concentrator photovoltaic, which can increase photoelectric conversion efficiency by approximately 3.1%, compared to an aluminum substrate.

This paper will refer briefly to some key aspects considered for the design of an Electrically HeatedPipe-in-Pipe- EHPIP system integrated to an Electric Submersible Pump-ESP, to be located at 1800 m water depth in the Campos Basin. In this system, under normal operation the well will be producing through the ESP and in case of long well shut in and during well restart up, a percentage of the electrical power will be delivered to heat the PIP system. The electrical system will have a common sub sea power cable and an Electrical Switch Module, to switch power alternatively to the heating system or to the pump. The systems will not operate simultaneously. (author)

The proposed is written as a senior undergraduate or the first-year graduate textbook,covering modern thermal devices such as heat sinks, thermoelectric generators and coolers, heatpipes, and heat exchangers as design components in larger systems. These devices are becoming increasingly important and fundamental in thermal design across such diverse areas as microelectronic cooling, green or thermal energy conversion, and thermal control and management in space, etc. However, there is no textbook available covering this range of topics. The proposed book may be used as a capstone design cours

We are building high temperature superconducting (HTS) current leads for a demonstration HTS-high gradient magnetic separation (HGMS) system cooled by a cryocooler. The current leads are entirely conductively cooled. A composite nitrogen heatpipe provides efficient thermal communication, and simultaneously electrical isolation, between the lead and an intermediate temperature heat sink. Data on the thermal and electrical performance of the heatpipe thermal intercept are presented. The electrical isolation of the heatpipe was measured as a function of applied voltage with and without a thermal load across the heatpipe. The results show the electrical isolation with evaporation, condensation and internal circulation taking place in the heatpipe.

The authors are building high temperature superconducting (HTS) current leads for a demonstration HTS high gradient magnetic separation (HGMS) system cooled by a cryocooler. The current leads are entirely conductively cooled. A composite nitrogen heatpipe provides efficient thermal communication, and simultaneously electrical isolation, between the lead and an intermediate temperature heat sink. Data on the thermal and electrical performance of the heatpipe thermal intercept are presented. The electrical isolation of the heatpipe was measured as a function of applied voltage with and without a thermal load across the heatpipe. The results show the electrical isolation with evaporation, condensation and internal circulation taking place in the heatpipe.

finite element method is applied to simulate transient temperature changes in pipe networks. The model is calculating time series data related to supply temperature to the DHN from heat production units, heat loads and return temperature related to each consumer to calculate dynamic temperature changes...... district heating networks [DHN] characteristics. This paper is presenting a new developed model, which reflects the thermo-dynamic behavior of DHN. It is designed for tree network topologies. The purpose of the model is to serve as a basis for applying a variety of scenarios towards lowering...... the temperature in DH systems. The main focus is on modeling transient heat transfer in pipe networks regarding the time delays between the heat supply unit and the consumers, the heat loss in the pipe networks and the consumers’ dynamic heat loads. A pseudo-dynamic approach is adopted and also the implicit...

The effects of different refrigerants on heat transfer performance of pulsating heatpipe (PHP) are investigated experimentally. The working temperature of pulsating heatpipe is kept in the range of 20°C-50°C. The startup time of the pulsating heatpipe with refrigerants can be shorter than 4 min, when heating power is in the range of 10W?100W. The startup time decreases with heating power. Thermal resistances of PHP with filling ratio 20.55% were obviously larger than those with other filling ratios. Thermal resistance of the PHP with R134a is much smaller than that with R404A and R600a. It indicates that the heat transfer ability of R134a is better. In addition, a correlation to predict thermal resistance of PHP with refrigerants was suggested.

National Aeronautics and Space Administration — Grooved aluminum/ammonia Constant Conductance HeatPipes (CCHPs) are the standard for thermal control in zero-gravity. Unfortunately, they are limited in terms of...

of low-energy DH systems. Various design concepts are considered in this paper: flexible pre-insulated twin pipes with symmetrical or asymmetrical insulation, double pipes, triple pipes. These technologies are potentially energyefficient and cost-effective solutions for DH networks in low-heat density......The synergy between highly energy efficient buildings and low-energy district heating (DH) systems is a promising concept for the optimal integration of energy saving policies and energy supply systems based on renewable energy (RE). Distribution heat losses represent a key factor in the design...... areas. We start with a review of theories and methods for steady-state heat loss calculation. Next, the article shows how detailed calculations with 2D-modeling of pipes can be carried out by means of computer software based on the finite element method (FEM). The model was validated by comparison...

Full Text Available In the present study, the specially designed grooved heatpipe charged with nanofluids was investigated in terms of various parameters such as heat transfer rate(50∼300W with 50 W interval, volume concentration(0.005%, 0.05%, 0.1%, and hybrid combinations, inclination(5°, 45°, 90°, cooling water temperature (1℃, 10℃, and 20℃, surface state, transient state and so on. Hybrid nanofluids with different volume concentration ratios with Ag-H2O and Al2O3-H2O were used as working fluids on a grooved heatpipe(GHP. Comparing with the pure water system, nanofluidic and hybrid nanofluidic system shows greater overall thermal resistance with increasing nano-particle concentration. Also hybrid nanofluids make the system deteriorate in terms of thermal resistance. The post nanofluid experimental data regarding GHP show that the heat transfer performance is similar to the results of nanofluid system. The thermal performance of a grooved heatpipe with nanofluids and hybrid nanofluids were varied with driving parameters but they led to worse system performance.

Full Text Available The effect of pipe flattening on heat transfer characteristics and the internal phenomena of a sintered-wick heatpipe has been investigated by using three-dimensional Finite Element Method. The calculation domains were focused at three important regions, i.e., vapor core, wick and wall. The Cartesian coordinates and the three-dimensional tetrahedral elements were applied in this model. The selected total elements were 638,400 to ensure the accuracy. The original diameter and total length of heatpipe were 6 mm and 200 mm, respectively. The composite wick made from sintered copper powder and grooved copper pipe was applied with water as working fluid. The vapor flow was assumed to be laminar and incompressible. The predicted results from the program were validated with the experimental results conducted with all similar controlled parameters. It was found that the predicted wall temperature and thermal resistance agreed well with the experimental data with the standard deviations of Â±5.95 and Â±32.85%, respectively. Furthermore, the overall thermal resistances of the tubular heatpipes (original diameter of 6 mm, which were flattened into the final thickness of 4.0 and 3.0 mm, decreased from 0.91 to 0.83Â°C/W due to an increase of the contacted surface for heat transfer surface. However, the overall thermal resistance of a flattened heatpipe with the final thickness of 2.5 mm increased to 0.88Â°C/W, resulting from drastic increase of pressure drop in narrower vapor core. The pivotal final thickness of flattened heatpipe, which is the minimum thickness of pipe to be flattened, has been analysed to be 2.75 mm (about 45% from original diameter.

In a Stirling radioisotope system, heat must continually be removed from the GPHS modules, to maintain the GPHS modules and surrounding insulation at acceptable temperatures. Normally, the Stirling convertor provides this cooling. If the Stirling engine stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS, but also ending the mission. An alkali-metal Variable Conductance HeatPipe (VCHP) was designed to allow multiple stops and restarts of the Stirling engine. A VCHP turns on with a delta T of 30 C, which is high enough to not risk standard ASRG operation but low enough to save most heater head life. This VCHP has a low mass, and low thermal losses for normal operation. In addition to the design, a proof-of-concept NaK VCHP was fabricated and tested. While NaK is normally not used in heatpipes, it has an advantage in that it is liquid at the reservoir operating temperature, while Na or K alone would freeze. The VCHP had two condensers, one simulating the heater head, and the other simulating the radiator. The experiments successfully demonstrated operation with the simulated heater head condenser off and on, while allowing the reservoir temperature to vary over 40 to 120 C, the maximum range expected. In agreement with previous NaK heatpipe tests, the evaporator delta T was roughly 70 C, due to distillation of the NaK in the evaporator.

One of the pitfalls of engineering education is to lose the physical insight of the problem while tackling the mathematical part. Forced convection heat transfer (the Graetz-Nusselt problem) certainly falls into this category. The equation of energy together with the equation of motion leads to a partial differential equation subject to various…

Full Text Available Today, the widespread application of cooling systems based on heatpipes makes significant contribution to the solution of the thermal control of electronic equipment. The use of heatpipes as heat transfer devices and heat exchanging equipment allows creating an efficient new-generation heat sinks. Nowadays, heatpipes are widely used in the following areas: electronic equipment, special application computer equipment (from small computers to large data centres, high power electronics. The article provides an analysis of the current state and prospects of heatpipes application in thermal control systems for ground-based electronic equipment.

Full Text Available This research aims to study the effect of evaporator temperature, pitch distance, and working fluid on the internal flow pattern and the heat transfer characteristics of the helical oscillating heatpipe. A Pyrex tube with an inner diameter of 2.4 mm was used to study the flow pattern in the evaporator section. The pitch distance varied at 1, 1.5, and 2 cm. Water and R-123 were used as working fluid with a filling ratio of 80% by total volume. In the evaporator section, the water temperature varied at 60, 75, and 90°C to supply heat to the heatpipe. In the condenser section, air with a temperature of 25°C was used as heat sink. From the results, it was found that 4 internal flow patterns, bubble flow, slug flow, annular flow, and stratified wavy flow, were observed in the evaporator section for both working fluids. The heat transfer rate decreased when the pitch distance was increased from 1 to 2 cm. The maximum heat flux was 2,132.6 and 1,773.4 W/m2 for the working fluid of R-123 and water, respectively. Both occurred at a pitch distance of 1 cm and an evaporator temperature of 90°C.

The development of the loop heatpipe technology for application in future space missions requires that certain aspects related to the operation of this device in regard to the heat transport, geometry and selected working fluid must be carefully considered. As efforts have been focused in the construction of loop heatpipes able to manage up to 80W of applied heat using an alternative working fluid, designing and testing these devices have shown important results. Two loop heatpipes have been built and tested, where they differ from each other on their compensation chamber geometry and use high grade acetone as working fluid, in substitution of the so-used ammonia. Life tests have shown reliable operation for both loop heatpipes with successful startups and continuous operation without temperature overshoot or evaporator dryout. The life tests results investigation have generated important data that has been applied on the design and construction of loop heatpipes toward their use in future space applications. (author)

The authors have developed a new type of heat spreader based on the integration of heatpipes directly within a thin planar structure suitable for use as a heat spreader or as the base layer in a substrate. The process uses micromachining methods to produce micron scale patterns that act as a wick in these small scale heatpipes. By using silicon or a low expansion metal as the wall material of these spreaders, they achieve a good match to the thermal coefficient of expansion of the die. The match allows the use of a thin high performance die attachment even on large size die. The embedded heatpipes result in high effective thermal conductivity for the new spreader technology.

NASA Glenn Research Center (GRC) has developed the LERCHP code. The PC-based LERCHP code can be used to predict the steady-state performance of heatpipes, including the determination of operating temperature and operating limits which might be encountered under specified conditions. The code contains a vapor flow algorithm which incorporates vapor compressibility and axially varying heat input. For the liquid flow in the wick, Darcy s formula is employed. Thermal boundary conditions and geometric structures can be defined through an interactive input interface. A variety of fluid and material options as well as user defined options can be chosen for the working fluid, wick, and pipe materials. This report documents the current effort at GRC to update the LERCHP code for operating in a Microsoft Windows (Microsoft Corporation) environment. A detailed analysis of the model is presented. The programming architecture for the numerical calculations is explained and flowcharts of the key subroutines are given

The high-speed oil-filled ball spinning and drawing process was put forward to manufacture the axially grooved heatpipe with highly efficient heat-transfer performance, and the forming mechanism of micro-grooves inside the pipe was investigated. The key factors influencing the configurations of micro-grooves were analyzed. When the spinning depth varies between 0.4 mm and 0.5 mm, drawing speed varies from 200 mm/min to 450 mm/min, rotary speed is beyond 6 000 r/min and working temperature is less than 50 ℃, the grooved tubes are formed with high quality and efficiency. The ball spinning process uses full oil-filling method to set up the steady dynamic oil-film that reduces the drawing force and improves the surface quality of grooved copper tube.

A part of the investigation is summarized of the thermal anomalies of the transmitter experiment package (TEP) on the Communications Technology Satellite (CTS) which were observed on four occasions in 1977. Specifically, the possible failure modes of the variable conductance heatpipe system (VCHPS) used for principal thermal control of the high-power traveling wave tube in the TEP are considered. Further, the investigation examines how those malfunctions may have given rise to the TEP thermal anomalies. Using CTS flight data information, ground test results, analysis conclusions, and other relevant information, the investigation concentrated on artery depriming as the most likely VCHPS failure mode. Included in the study as possible depriming mechanisms were freezing of the working fluid, Marangoni flow, and gas evolution within the arteries. The report concludes that while depriming of the heatpipe arteries is consistent with the bulk of the observed data, the factors which cause the arteries to deprime have yet to be identified.

Slush fluids, such as slush hydrogen and slush nitrogen, are two-phase (solid-liquid) single-component cryogenic fluids containing solid particles in a liquid, and consequently their density and refrigerant capacity are greater than for liquid state fluid alone. This paper reports on the experimental results of the forced convection heat transfer characteristics of slush nitrogen flowing in a pipe. Heat was supplied to slush nitrogen by a heater wound around the copper pipe wall. The local heat transfer coefficient was measured in conjunction with changes in the velocity and the solid fraction. The differences in heat transfer characteristics between two-phase slush and single phase liquid nitrogen were obtained, and the decrease in heat transfer to slush nitrogen caused by the previously observed pressure drop reduction was confirmed by this study. Furthermore, for the purpose of establishing the thermal design criteria for slush nitrogen in the case of pressure drop reduction, the heat transfer correlation between the experimental results and the Sieder-Tate Equation was obtained.

High-temperature heatpipes are being evaluated for use in energy conversion applications such as fuel cells, gas turbine re-combustors, Stirling cycle heat sources; and with the resurgence of space nuclear power both as reactor heat removal elements and as radiator elements. Long operating life and reliable performance are critical requirements for these applications. Accordingly, long-term materials compatibility is being evaluated through the use of high-temperature life test heatpipes. Thermacore, Inc., has carried out a sodium heatpipe 10-year life test to establish long-term operating reliability. Sodium heatpipes have demonstrated favorable materials compatibility and heat transport characteristics at high operating temperatures in air over long time periods. A representative one-tenth segment Stirling Space Power Converter heatpipe with an Inconel 718 envelope and a stainless steel screen wick has operated for over 87,000 hr (10 yr) at nearly 700 C. These life test results have demonstrated the potential for high-temperature heatpipes to serve as reliable energy conversion system components for power applications that require long operating lifetime with high reliability. Detailed design specifications, operating history, and post-test analysis of the heatpipe and sodium working fluid are described.

We are developing a highly conductive flat heatpipe (called Thermal Ground Plane or TGP) for cooling computer chips. Conventional heatpipes have circular cross sections and thus can't make good contact with chip surface. The flatness of our TGP will enable conformal contact with the chip surface and thus enhance cooling efficiency. Another limiting factor in conventional heatpipes is the capillary flow of the working fluid through a wick structure. In order to overcome this limitation we have created a highly porous wick structure on a flat titanium substrate by using micro fabrication technology. We first etch titanium to create very tall micro pillars with a diameter of 5 μm, a height of 40 μm and a pitch of 10 μm. We then grow a very fine nano structured titania (NST) hairs on all surfaces of the pillars by oxidation in H202. In this way we achieve a wick structure which utilizes multiple length scales to yield high performance wicking of water. It's capable of wicking water at an average velocity of 1 cm/s over a distance of several cm. A titanium cavity is laser-welded onto the wicking substrate and a small quantity of water is hermetically sealed inside the cavity to achieve a TGP. The thermal conductivity of our preliminary TGP was measured to be 350 W/m-K, but has the potential to be several orders of magnitude higher.

The temperature distribution across a flat heatpipe sandwich structure, subjected to an intense localized thermal flux has been investigated both experimentally and computationally. The aluminum sandwich structure consisted of a pair of aluminum alloy face sheets, a truncated square honeycomb (cruciform) core, a nickel metal foam wick and distilled water as the working fluid. Heat was applied via a propane torch to the evaporator side of the flat heatpipe, while the condenser side was cooled via natural convective and radiative heat transfer. A novel method was developed to estimate experimentally, the heat flux distribution of the torch on the evaporator side. This heat flux distribution was modeled using a probability function and validated against the experimental data. Applying the estimated heat flux distribution as the surface boundary condition, a finite volume analysis was performed for the wall, wick and vapor core regions of the flat heatpipe to obtain the field variables in these domains. The results were found to agree well with the experimental data indicating the thermal spreading effect of the flat heatpipe. (author)

Nuclear energy generated in fission reactors is a versatile commodity that can, in principle, satisfy any and all of mankind's energy needs through direct or indirect means. In addition to its dominant current use for electricity generation and, to a lesser degree, marine propulsion, nuclear energy can and has been used for process heat applications, such as space heating, industrial process heating and seawater desalination. Moreover, a wide variety of reactor designs has been employed to this end in a range of countries. From this spectrum of experience, two design approaches emerge for nuclear process heating (NPH): extracting a portion of the thermal energy from a nuclear power plant (NPP) (i.e., creating a combined heat and power, or CHP, plant) and transporting it to the user, or deploying dedicated nuclearheating plants (NHPs) in generally closer proximity to the thermal load. While the former approach is the basis for much of the current NPH experience, considerable recent interest exists for the latter, typically involving small, innovative reactor plants with enhanced and passive safety features. The high emphasis on inherent nuclear safety characteristics in these reactor designs reflects the need to avoid any requirement for evacuation of the public in the event of an accident, and the desire for sustained operation and investment protection at minimum cost. Since roughly 67% of mankind's primary energy usage is not in the form of electricity, a vast potential market for NPH systems exists, particularly at the low-to-moderate end-use temperatures required for residential space heating and several industrial applications. Although only About 0.5% of global nuclear energy production is presently used for NPH applications, an expanded role in the 21st century seems inevitable, in part, as a measure to reduce greenhouse gas emissions and improve air quality. While the technical aspects of many NPH applications are considered to be well proven, a

Nuclear energy generated in fission reactors is a versatile commodity that can, in principle, satisfy any and all of mankind's energy needs through direct or indirect means. In addition to its dominant current use for electricity generation and, to a lesser degree, marine propulsion, nuclear energy can and has been used for process heat applications, such as space heating, industrial process heating, and seawater desalination. Moreover, a wide variety of reactor designs has been employed to this end in a range of countries. From this spectrum of experience, two design approaches emerge for nuclear process heating, (NPH): extracting a portion of the thermal energy from a nuclear power plant (NPP) (i.e., creating a combined heat and power, or CHP, plant) and transporting it to the user, or deploying dedicated nuclearheating plants (NHPs) in generally closer proximity to the thermal load. While the former approach is the basis for much of the current NPH experience, considerable recent interest exists for the latter, typically involving small, innovative reactor plants with enhanced and passive safety features. The high emphasis on inherent nuclear safety characteristics in these reactor designs reflects the need to avoid any requirement for evacuation of the public in the event of an accident, and the desire for sustained operation and investment protection at minimum cost. Since roughly 67% of mankind's primary energy usage is not in the form of electricity, a vast potential market for NPH systems exists, particularly at the low-to-moderate end-use temperatures required for residential space heating, and several industrial applications. Although only about 0.5% of global nuclear energy production is presently used for NPH applications, an expanded role in the 21st century seems inevitable, in part, as a measure to reduce greenhouse gas emissions and improve air quality. While the technical aspects of many NPH applications are considered to be well proven

Full Text Available The addition of the nanoparticles to the base fluid is one of the significant issues to enhance the heat transfer of heatpipes. The purpose of this review is to summarize the research done on heatpipes using nanofluids as working fluids in recent years (2012 to 2013. The peer reviewed papers published in citation index journals have been selected for review in this paper. This review article provides additional information for the design of heatpipes with optimum conditions regarding the heat transfer characteristics of nanofluids in heatpipes. Moreover, this paper identifies several important issues that should be considered further in future works.

A numerical model is developed to simulate the transient performance characteristics of loop heatpipes (LHP). The model satisfactorily simulates the overall dynamic behavior of an LHP unit tested under ambient and vacuum environments. The startup phase is also reproduced using the experimentally obtained incipient wall superheat. The accurate heat leak predictions at low powers remain problematic and experimental correlation is necessary. The model can be used to analyze the dynamic behavior of an LHP based thermal control system exposed to transient thermal loads.

Novel hybrid wick heatpipes are developed to operate against gravity on planetary surfaces, operate in space carrying power over long distances and act as thermosyphons on the planetary surface for Lunar and Martian landers and rovers. These hybrid heatpipes will be capable of operating at the higher heat flux requirements expected in NASA's future spacecraft and on the next generation of polar rovers and equatorial landers. In addition, the sintered evaporator wicks mitigate the start-up problems in vertical gravity aided heatpipes because of large number of nucleation sites in wicks which will allow easy boiling initiation. ACT, NASA Marshall Space Flight Center, and NASA Johnson Space Center, are working together on the Advanced Passive Thermal experiment (APTx) to test and validate the operation of a hybrid wick VCHP with warm reservoir and HiK"TM" plates in microgravity environment on the ISS.

Full Text Available The present paper proposes the analysis and the simulation of the convection heat transfer into the fluid flow with turbulence promoters utilizing heatpipes. The study is based on the necesity of the unconventional energy forms capitalization, increasing of the energy efficiency and leads to the energy consumtion decrease in concordance with the sustainable development concept.

Thermoelectric refrigeration always presents a heat flux addressing problem (constriction resistance) and it is a subject that has extensively been studied and analysed [closed form equation for thermal constriction/spreading resistances with variable resistances boundary conditions, IEPS Conference, 1994]. In previous works [Issues of the heat dissipation coming from a big surface through a much smaller one, 20th International Conference on Thermoelectrics, Beijing-China, 2001], a device (flat heatpipe) capable of addressing the heat flux has been theoretically and experimentally developed to reduce the so called constriction resistance (the lower the constriction resistance the higher the thermoelectric module performance). This work presents the experimental results of the constriction resistance for different prototypes of flat heatpipe and investigates if they are in agreement with the theoretical predictions. It also shows the influence of certain parameters on the constriction resistance. The results have later been compared with those obtained for a flat plate in order to check whether or not the device improves the thermoelectric module performance. A brief description of the device operation is also given. (Author)

pipe wall. This is not likely to be the case in the thin wicks used in most heatpipes unless severe dryout occurs. Eninger [7] studied the capillary...balance on a randomly oriented fibecr. The theoretical model required an empirical constant obtained from the experimental results. Eninger also 6...structure was utilized for this experimpnt. The two-component wick structure was utilized previously by Eninger [7], who was able to measure slight

Geothermal heatpipes are an effective heat source for heat pumps used for space heating. Because the area for the installation of borehole heat exchangers is limited in urban areas (one site per borehole), the maximum heat extractable from one borehole shall rise. In cooperation with the FKW Hannover, the Institute for Thermodynamics of the Leibniz University of Hannover is investigating the thermodynamic behavior of CO2 driven geothermal heatpipes of higher thermal power. Therefore two different types of geothermal heatpipes with a length of 400 m each have been installed. Furthermore a numerical simulation of the heat and mass transfer within the pipes is under development. The experimental setup and first results of the experiments are presented as well as the current status of the numerical simulation. A comparison of the two different types of heatpipes and a comparison of the experimental data with the numerical simulation is given.

Proper heat transfer management is important to key electronic components in microelectronic applications. Pulsating heatpipes (PHP) can be an efficient solution to such heat transfer problems. However, mathematical modelling of a PHP system is still very challenging, due to the complexity and multiphysics nature of the system. In this work, we present a simplified, two-phase heat transfer model, and our analysis shows that it can make good predictions about startup characteristics. Furthermore, by considering parameter estimation as a nonlinear constrained optimization problem, we have used the firefly algorithm to find parameter estimates efficiently. We have also demonstrated that it is possible to obtain good estimates of key parameters using very limited experimental data.

The orientation of the heatpipe plays the significant role in its performance. In specific orientations, the performance of the heatpipe is directly related to the wick structure. In conventional heatpipe, the working fluid is used a negative surface-tension gradient with temperature. It is an unfavorable one and it decreases the heat transport between the evaporator section and the condenser section. An Aqueous solution of n-Pentanol having a positive surface tension gradient with temperature is suggested as a working medium for heatpipe to improve the performance of capillary limit and operating stability. The objective of this paper is to perform a comparative study of heatpipe performance using the aqueous solution of n-Pentanol with water at various inclinations. The results are presented to demonstrate the merits and suitability of the aqueous solution of n-Pentanol as a working fluid for heatpipe.

A grooved heatpipe (GHP) is an important device for managing heat in space applications such as satellites and space stations, as it works efficiently in the absence of gravity. Apart from the above application, axial GHPs are used in many applications, such as electronic cooling units for temperature control and permafrost cooling. Improving the performance of GHPs is essential for better cooling and thermal management. In the present study, the effect of anodization on the heat transfer characteristics of a GHP is studied with R600a as a working fluid. In addition, the effects of fill ratio, inclination angle and heat inputs on the heat transfer performance of a GHP are studied. Furthermore, the effect of heat flux on dimensional numbers, such as the Webber, Bond, Kutateladze and condensation numbers, are studied. The inclination angle, heat input and fill ratio of GHPs are varied in the range of 0°-90°, 25-250 W and 10-70 % respectively. It is found that the above parameters have a significant effect on the performance of a GHP. Due to the anodisation, the maximum enhancement in heat transfer coefficient at the evaporator is 39 % for a 90° inclination at a heat flux of 11 kW/m2. The reported performance enhancement of a GHP may be due to the large numbers of nucleation sites created by the anodisation process and enhancement in the capillary force due to the coating.

A grooved heatpipe (GHP) is an important device for managing heat in space applications such as satellites and space stations, as it works efficiently in the absence of gravity. Apart from the above application, axial GHPs are used in many applications, such as electronic cooling units for temperature control and permafrost cooling. Improving the performance of GHPs is essential for better cooling and thermal management. In the present study, the effect of anodization on the heat transfer characteristics of a GHP is studied with R600a as a working fluid. In addition, the effects of fill ratio, inclination angle and heat inputs on the heat transfer performance of a GHP are studied. Furthermore, the effect of heat flux on dimensional numbers, such as the Webber, Bond, Kutateladze and condensation numbers, are studied. The inclination angle, heat input and fill ratio of GHPs are varied in the range of 0°-90°, 25-250 W and 10-70 % respectively. It is found that the above parameters have a significant effect on the performance of a GHP. Due to the anodisation, the maximum enhancement in heat transfer coefficient at the evaporator is 39 % for a 90° inclination at a heat flux of 11 kW/m2. The reported performance enhancement of a GHP may be due to the large numbers of nucleation sites created by the anodisation process and enhancement in the capillary force due to the coating.

To reduce the influence of the pipe material on the measurement of effective thermal conductivity, the pipe of a cryogenic pulsating heatpipe is generally made of stainless steel. Because of the low thermal conductivity of stainless steel, the pre-cooling of the evaporator in cryogenic pulsating heatpipe using helium as working fluid at 4.2 K is a problem. We designed a mechanical-thermal switch between the cryocooler and the evaporator, which was on during the pre-cooling process and off during the test process. By using the pre-cooling system, the cool down time of the cryogenic pulsating heatpipe was reduced significantly.

National Aeronautics and Space Administration — The thermal transport requirements for future spacecraft missions continue to increase, approaching several kilowatts. At the same time the heat acquisition areas...

The purpose of this study is to investigate on the experimental verification analysis for the pipe whip problems and to obtain the quantitative evaluation technologies for the design technique of pipe whip restraints. These will contribute to the advance of nuclear regulatory technologies and enhance nuclear power plant safety. This study presents the experimental and transient analytical results of pipe whip tests using the 4', 6' diameter pipe and U-shaped restraints. In the tests, the effects of the overhang length, clearance, impact height on the pipe whip behavior of the pipe-restraints were investigated. The transient impact analysis of the pipe-restraint system was conducted by the finite element program ABAQUS. The applicability of the ABAQUS program to the pipe whip analysis is made clear through this analysis.

advantage of renewable energy. The results showed that the energy consumption was 3% less in the 2-pipe chilled beam system in comparison with the conventional 4-pipe system when moving cooled and heated water through the building, transferring the energy to where it is needed. Using free cooling (taking...... consumption and hence energy savings in the 2-pipe chilled beam system in comparison with the 4-pipe system. The 2-pipe chilled beam system used high temperature cooling and low temperature heating with a water temperature of 20°C to 23°C, available for free most of the year. The system can thus take......Simulations were performed to compare a conventional 4-pipe chilled beam system and a 2-pipe chilled beam system. The objective was to establish requirements, possibilities and limitations for a well-functioning 2-pipe chilled beam system for both cooling and heating of office buildings...

In a Stirling radioisotope system, heat must continually be removed from the GPHS modules, to maintain the GPHS modules and surrounding insulation at acceptable temperatures. Normally, the Stirling convertor provides this cooling. If the Stirling engine stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS, but also ending the mission. An alkali-metal Variable Conductance HeatPipe (VCHP) was designed to allow multiple stops and restarts of the Stirling engine. A VCHP was designed for the Advanced Stirling Radioisotope Generator, with a 850 °C heater head temperature. The VCHP turns on with a ΔT of 30 °C, which is high enough to not risk standard ASRG operation but low enough to save most heater head life. This VCHP has a low mass, and low thermal losses for normal operation. In addition to the design, a proof-of-concept NaK VCHP was fabricated and tested. While NaK is normally not used in heatpipes, it has an advantage in that it is liquid at the reservoir operating temperature, while Na or K alone would freeze. The VCHP had two condensers, one simulating the heater head, and the other simulating the radiator. The experiments successfully demonstrated operation with the simulated heater head condenser off and on, while allowing the reservoir temperature to vary over 40 to 120 °C, the maximum range expected. In agreement with previous NaK heatpipe tests, the evaporator ΔT was roughly 70 °C, due to distillation of the NaK in the evaporator.

In this paper, fully developed convective heat transfer of viscoelastic flow in a curved pipe under the constant heat flux at the wall is investigated analytically using a perturbation method. Here, the curvature ratio is used as the perturbation parameter and the Oldroyd-B model is applied as the constitutive equation. In the previous studies, the Dirichlet boundary condition for the temperature at the wall has been used to simplify the solution, but here exactly the non-homogenous Neumann boundary condition is considered to solve the problem. Based on this solution, the non-axisymmetric temperature distribution of Dean flow is obtained analytically and the effect of flow parameters on the flow field is investigated in detail. The current analytical results indicate that increasing the Weissenberg number, viscosity ratio, curvature ratio, and Prandtl number lead to the increase of the heat transfer in the Oldroyd-B fluid flow. (orig.)

The very high heat flux dissipated by a Central Processing Unit (CPU) can no longer be handled by a conventional, single-phased cooling system. Thermal management of a CPU is now moving towards two-phase systems to maintain CPUs below their maximum temperature. A heatpipe is one of the emerging cooling systems to address this issue because of its superior efficiency and energy input independence. The goal of this research is to improve the performance of a heatpipe by integrating a biomaterial as the wick structure. In this work, the heatpipe was made from copper pipe and the biomaterial wick structure was made from tabulate coral with a mean pore diameter of 52.95 μm. For comparison purposes, the wick structure was fabricated from sintered Cu-powder with a mean pore diameter of 58.57 µm. The working fluid for this experiment was water. The experiment was conducted using a processor as the heat source and a plate simulator to measure the heat flux. The utilization of coral as the wick structure can improve the performance of a heatpipe and can decrease the temperature of a simulator plate by as much as 38.6 % at the maximum heat load compared to a conventional copper heat sink. This method also decreased the temperature of the simulator plate by as much as 44.25 °C compared to a heatpipe composed of a sintered Cu-powder wick.

The very high heat flux dissipated by a Central Processing Unit (CPU) can no longer be handled by a conventional, single-phased cooling system. Thermal management of a CPU is now moving towards two-phase systems to maintain CPUs below their maximum temperature. A heatpipe is one of the emerging cooling systems to address this issue because of its superior efficiency and energy input independence. The goal of this research is to improve the performance of a heatpipe by integrating a biomaterial as the wick structure. In this work, the heatpipe was made from copper pipe and the biomaterial wick structure was made from tabulate coral with a mean pore diameter of 52.95 μm. For comparison purposes, the wick structure was fabricated from sintered Cu-powder with a mean pore diameter of 58.57 µm. The working fluid for this experiment was water. The experiment was conducted using a processor as the heat source and a plate simulator to measure the heat flux. The utilization of coral as the wick structure can improve the performance of a heatpipe and can decrease the temperature of a simulator plate by as much as 38.6 % at the maximum heat load compared to a conventional copper heat sink. This method also decreased the temperature of the simulator plate by as much as 44.25 °C compared to a heatpipe composed of a sintered Cu-powder wick.

National Aeronautics and Space Administration — Thermal control systems are sized for the maximum heat load in the warmest continuous environment. This design process results in a larger radiator surface area than...

Experimental results show conclusively that the presence of a small quantity of a noncondensable gas (NCG) mixed with the working fluid has a considerable effect on the condensation process in a rotating heatpipe. The temperature distribution in the condenser shows the blanketing effect of the NCG and the ratio of the molecular weight of the working fluid to that of the NCG has a very definite effect on the shape of this distribution. Some of the effects are quite similar to the well-established data on stationary heatpipes.

The principal concepts related to the nature of the processes occurring in high-temperature heatpipes with a noncondensable gas are examined, and guidelines for the development of such heatpipes are presented. The discussion is illustrated by experimental results obtained for a horizontal sodium heatpipe (diameter, 18/1 mm; length, 710 mm). In particular, attention is given to the starting dynamics and mechanisms, the shape of the vapor-gas front, and the vapor-gas front velocity.

Experiments were performed for investigation of the long term performance of mild-steel heatpipes. Working fluids were a NaCr solution in water, as well as water. The test period covered approximately 15,000 h. It is concluded that both types of heatpipes perform well; the performance of the heatpipe containing the NaCr solution, however, is superior. (author)

An experimental investigation has been carried out to examine the thermal, performance of a sintered wick heatpipe using aqueous graphene nanoplatelets (GNP) nanofluids. The study focuses on changes in the effects of GNP concentration, heatpipe inclination angle and input heating power. The max...

Full Text Available Heat transfer and fluid flow in the heatpipe system result in thermodynamic irreversibility generating entropy. The minimum entropy generation principle can be used for optimum design of flat heatpipe. The objective of the present work is to minimise the total entropy generation rate as the objective function with different parameters of the flat heatpipe subjected to some constraints. These constraints constitute the limitations on the heat transport capacity of the heatpipe. This physical nonlinear programming problem with nonlinear constraints is solved using LINGO 15.0 software, which enables finding optimum values for the independent design variables for which entropy generation is minimum. The effect of heat load, length, and sink temperature on design variables and corresponding entropy generation is studied. The second law analysis using minimum entropy generation principle is found to be effective in designing performance enhanced heatpipe.

The possibility of using Vermont Yankee condenser effluent for commercial food growth enhancement was examined. It was concluded that for the Vermont Yankee Nuclear Station, commercial success, both for horticulture and aquaculture endeavors, could not be assured without additional research in both areas. This is due primarily to two problems. First, the particularly low heat quality of our condenser discharge, being nominally 72 +- 2/sup 0/F; and second, to the capital intensive support systems. The capital needed for the support systems include costs of pumps, piping and controls to move the heated water to growing facilities and the costs of large, efficient heat exchangers that may be necessary to avoid regulatory difficulties due to the 1958 Delaney Amendment to the U.S. Food, Drug and Cosmetics Act. Recommendations for further work include construction of a permanent aquaculture research laboratory and a test greenhouse complex based on a greenhouse wherein a variety of heating configurations would be installed and tested. One greenhouse would be heated with biogas from an adjacent anaerobic digester thermally boosted during winter months by Vermont Yankee condenser effluent. The aquaculture laboratory would initially be dedicated to the Atlantic salmon restoration program. It appears possible to raise fingerling salmon to smolt size within 7 months using water warmed to about 60/sup 0/F. The growth rate by this technique is increased by a factor of 2 to 3. A system concept has been developed which includes an aqua-laboratory, producing 25,000 salmon smolt annually, a 4-unit greenhouse test horticulture complex and an 18,000 square foot commercial fish-rearing facility producing 100,000 pounds of wet fish (brook trout) per year. The aqualab and horticulture test complex would form the initial phase of construction. The trout-rearing facility would be delayed pending results of laboratory studies confirming its commercial viability.

Research has shown that the risk of hot spots in the drinking water pipes is very high. Hot spots are, for example, caused by central heatingpipes that are too close to the water pipes. The water pipes may be 25 C for a long period, thus creating the risk of legionella growth. The various disciplines need to be careful in the design stage and building stage to prevent such situations from occurring. [Dutch] Onderzoek heeft uitgewezen dat het risico op 'hotspots' in de drinkwaterleidingen erg groot is. Hotspots worden bijvoorbeeld veroorzaakt door cv-leidingen die te dicht in de buurt van waterleidingen lopen. Die waterleidingen kunnen dan langdurig warmer zijn dan 25C en daardoor gevaar opleveren voor legionellagroei. Het vereist zorg van meerdere disciplines in de ontwerpfase en de bouwfase om deze situaties te vermijden.

Full Text Available In this paper, heat transfer performance of a 40 cm-length circular heatpipe with screen mesh wick is experimentally investigated. This heatpipe is made of copper with two diameters; larger in the evaporator and smaller in the adiabatic and condenser. Three different liquids including water, methanol, and ethanol are separately filled within the heatpipe. Low heat fluxes are applied (up to 2500 W/m2 in the evaporator and constant temperature water bath is used at three levels including 15, 25, and 35 °C in the condenser. Results demonstrate that higher heat transfer coefficients are obtained for water and ethanol in comparison with methanol. Furthermore, increasing heat flux increases the evaporator heat transfer coefficient. For the case of methanol, some degradation in heat transfer coefficient is occurred at high heat fluxes which can be due to the surface dryout effect. Increasing the inclination angle decreases the heatpipe thermal resistance.

As part of an effort to identify cost efficient fabrication techniques for Loop HeatPipe (LHP) construction, NASA Goddard Space Flight Center's Cryogenics and Fluids Branch collaborated with the U.S. Naval Academy s Aerospace Engineering Department in Spring 2012 to investigate the viability of carbon foam as a wick material within LHPs. The carbon foam was manufactured by ERG Aerospace and machined to geometric specifications at the U.S. Naval Academy s Materials, Mechanics and Structures Machine Shop. NASA GSFC s Fractal Loop HeatPipe (developed under SBIR contract #NAS5-02112) was used as the validation LHP platform. In a horizontal orientation, the FLHP system demonstrated a heat flux of 75 Watts per square centimeter with deionized water as the working fluid. Also, no failed start-ups occurred during the 6 week performance testing period. The success of this study validated that foam can be used as a wick structure. Furthermore, given the COTS status of foam materials this study is one more step towards development of a low cost LHP.

This article made experimental study on mini-axial grooved heatpipes (AGHP) with 11 flattening forms. It analyzed how the flattening form, flattening thickness and working temperature affect axial tem-perature distribution, thermal resistance, heat transfer limit and the phase-change heat transfer coeffi-cients in evaporator and condenser sections. The result indicates that all forms of AGHPs can maintain good isothermal performance under normal operating condition. The geometric shape of AGHP has obvious impact on heat transfer limit. With respect to an AGHP with 2 mm-thick evaporator section, when the thickness of its condenser section increases from 2 to 3 mm, its heat transfer limit increases by 81%; with respect to an AGHP with 3 mm-thick evaporator section, when the thickness of its con-denser section increases from 2 to 3 mm, its heat transfer limit increases by 134%; with respect to an AGHP with 4 mm-thick condenser section, when the thickness of its evaporator section increases from 2 to 3 mm, its heat transfer limit increases by 26%. When the thickness of the evaporator section in-creases by 1 mm, the heat transfer limit will increase by 9%-26%, while when the thickness of the condenser section increases by 1 mm, the heat transfer limit will increase by 20%-86%. The thickness of the condenser section has greater impact on heat transfer performance of an AGHP than the thick-ness of the evaporator section does. The study content of this article will help understand the heat transfer performance of AGHP, and electronic thermal design process.

National Aeronautics and Space Administration — Increasing thermal requirements for space-based thermal control systems are straining the capabilities of conventional heatpipes. Mainstream has experimentally...

A mathematical model is developed of excess liquid in heatpipes that is used to calculate the parameters governing the axial flow of liquid in fillets and puddles that form in vapor spaces. In an acceleration field, the hydrostatic pressure variation is taken into account, which results in noncircular meniscus shapes. The two specific vapor-space geometries considered are circular and the 'Dee-shape' that is formed by a slab wick in a circular tube. Also presented are theoretical and experimental results for the conditions under which liquid slugs form at the ends of the vapor spaces. These results also apply to the priming of arteries.

Data in the literature on heat transfer in the case of nucleate boiling of various liquids in the wicks of heatpipes are reviewed. It is shown that none of the known analytical relationships can be used to generalize, with sufficient accuracy, the experimental data found in the literature. It is further shown that the exponent of the specific heat flux in the heat transfer law changes as a function of the liquid and wick properties. A relationship is obtained which generalizes experimental data for heat transfer agents of moderate temperatures (water, acetone, ethanol, and R-11 and R-113 coolants) and ammonia.

This study deals with global best algorithm based thermal design of spiral heat exchangers and heatpipes. Spiral heat exchangers are devices which are highly efficient in extremely dirty and fouling process duties. Spirals inherent in design maintain high heat transfer coefficients while avoiding hazardous effects of fouling and uneven fluid distribution in the channels. Heatpipes have wide usage in industry. Thanks to the two phase cycle which takes part in operation, they can transfer high amount of heat with a negligible temperature gradient. In this work, a new stochastic based optimization method global best algorithm is applied for multi objective optimization of spiral heat exchangers as well as single objective optimization for heatpipes. Global best algorithm is easy-to-implement, free of derivatives and it can be reliably applied to any optimization problem. Case studies taken from the literature approaches are solved by the proposed algorithm and results obtained from the literature approaches are compared with thosed acquired by GBA. Comparisons reveal that GBA attains better results than literature studies in terms of solution accuracy and efficiency.

Requirements for the wall thickness of the casing pipes in Europe were formulated to clarify the laying conditions, representative for the European district heating areas. We achieved a broad estimate by defining four scenarios for the laying of district heatingpipes. It is common to the four scenarios that that all bends, branches etc. are always laid in sand. The four scenarios are differentiated by soil types. The soil types include: Uniform sand, Well graded gravel, Sand with fines and Sand with crushed stone. In the following analysis it was possible to examine the influence from following parameters: Casing thickness; Diameter of steel pipe; Diameter of casing; Material properties (PUR and PE); Soil type. The results from the model showed that uniform sand is the absolute best soil type. Based on the results from and earlier project a laboratory method has been developed. The result was a test method based on the indentation of three mandrels with a diameter of {phi}30 mm with a taper with an angle of 45 deg. and with roundings on the apex of R5 mm, R10 mm and R15 mm, respectively. The mandrels simulate stones. The examinations among other things showed that even a 1.5 mm casing demands an indentation of 20 mm with a R5 mm mandrel before it is perforated. The demanded force is 1.6 kN, which is considerably higher than the theoretically highest force in an actual situation. On this background it is recommended that the minimum requirement for the wall thickness of the casings with diameters less than 200 mm should still follow the EN 253, whereas the minimum requirement for the larger casing pipes securely can be reduced. Based on the tests and an evaluation of the safety factors it is proposed that the wall thickness for the largest pipes can be reduced 50%. Thus the wall thickness of an 800 mm casing should be 6.6 mm with a linear reduction down to 3 mm for 180 mm casing. (EG)

and smart gas grids. Improving DH pipes by improving the insulation standard results in decreasing the heat and temperature losses from the pipe networks. When reducing heat losses from DH pipes, there is a trade-off between the increasing cost of pipe insulation and the associated savings in the heat......Reducing heat losses from the pipe networks in district heating (DH) systems is one of the main challenges when developing DH in the future. Fourth generation DH is a concept that defines the role of DH in future smart energy systems as an integrated part together with smart electricity grids...... by implementing different pipe insulation standards. In the second step, the specific grid losses found in the first step are analysed in an integrated energy systems model where all main energy sectors and their interrelations are included. The outcome of the study can provide decision support when planning...

The high fossil energy consumption not only causes the scarcity of energy but also raises problems of global warming. Increasing needs of fossil fuel could be reduced through the utilization of solar energy by using solar collectors. Indonesia has the abundant potential for solar energy, but non-renewable energy sources still dominate energy consumption. With heatpipe as passive heat transfer device, evacuated tube solar collector is expected to heat up water for industrial and home usage without external power supply needed to circulate water inside the solar collector. This research was conducted to determine the performance of heatpipe-based evacuated tube solar collector as solar water heater experimentally. The experiments were carried out using stainless steel screen mesh as a wick material, and water and Al2O3-water 0.1% nanofluid as working fluid, and applying inclination angles of 0°, 15°, 30°, and 45°. To analyze the heat absorbed and transferred by the prototype, water at 30°C was circulated through the condenser. A 150 Watt halogen lamp was used as sun simulator, and the prototype was covered by an insulation box to obtain a steady state condition with a minimum affection of ambient changes. Experimental results show that the usage of Al2O3-water 0.1% nanofluid at 30° inclination angle provides the highest thermal performance, which gives efficiency as high as 0.196 and thermal resistance as low as 5.32 °C/W. The use of nanofluid as working fluid enhances thermal performance due to high thermal conductivity of the working fluid. The increase of the inclination angle plays a role in the drainage of the condensate to the evaporator that leads to higher thermal performance until the optimal inclination angle is reached.

A loop heatpipe (LHP) is a very versatile heat transfer device which can transport a large heat load over a long distance with a small temperature difference. All LHPs currently servicing orbiting spacecraft are designed to operate in the room temperature range. Future space telescopes and space-based Earth resource imaging satellites require passive cryogenic heat transport devices that can thermally couple remote cryocoolers to sensor or instrument of interest while providing the capability of payload vibration/jitter isolation, implementation of redundant coolers, and coupling of multiple sensors to a common heat sink. All of these requirements can be satisfied by using a cryogenic LHP (CLHP). Although the development of CLHPs faces several technical challenges, NASA Goddard Space Flight Center has devoted extensive efforts in developing CLHP technology over the past decade and has made significant progress. In particular, the combination of the innovative ideas of using a secondary capillary pump to manage the parasitic heat gain and using a hot reservoir to reduce the system pressure under the ambient condition has led to the successful development of the CLHP. Several CLHPs charged with nitrogen and hydrogen were built and tested in thermal vacuum chambers. These CLHPs demonstrated reliable start-up and robust operation during power cycle and sink temperature cycle tests.

This study was inspired to investigate an alternative cooling system using a helium-based pulsating heatpipes (PHP), for low temperature superconducting magnets. In addition, the same approach can be used for exploring other low temperature applications. The advantages of PHP for transferring heat and smoothing temperature profiles in various room temperature applications have been explored for the past 20 years. An experimental apparatus has been designed, fabricated and operated and is primarily composed of an evaporator and a condenser; in which both are thermally connected by a closed loop capillary tubing. The main goal is to measure the heat transfer properties of this device using helium as the working fluid. The evaporator end of the PHP is comprised of a copper winding in which heat loads up to 10 watts are generated, while the condenser is isothermal and can reach 4.2 K via a two stage Sumitomo RDK408A2 GM cryocooler. Various experimental design features are highlighted. Additionally, performance results in the form of heat transfer and temperature characteristics are provided as a function of average condenser temperature, PHP fill ratio, and evaporator heat load. Results are summarized in the form of a dimensionless correlation and compared to room temperature systems. Implications for superconducting magnet stability are highlighted.

A loop heatpipe (LHP) is a very versatile heat transfer device that can transport a large heat load over a long distance with a small temperature difference. All LHPs currently servicing orbiting spacecraft are designed to operate in the room temperature range. Future space telescopes and space-based Earth resource imaging satellites require passive cryogenic heat transport devices that can thermally couple remote cryocoolers to sensor or instrument of interest while providing the capability of payload vibration jitter isolation, implementation of redundant coolers, and coupling of multiple sensors to a common heat sink. All of these requirements can be satisfied by using a cryogenic LHP (CLHP). Although the development of CLHPs faces several technical challenges, NASA Goddard Space Flight Center has devoted extensive efforts in developing CLHP technology over the past decade and has made significant progress. In particular, the combination of the innovative ideas of using a secondary capillary pump to manage the parasitic heat gain and using a hot reservoir to reduce the system pressure under the ambient condition has led to the successful development of the CLHP. Several CLHPs charged with nitrogen and hydrogen were built and tested in thermal vacuum chambers. These CLHPs demonstrated reliable start-up and robust operation during power cycle and sink temperature cycle tests.

Test results on a modular simulation of the thermal transport and heat storage characteristics of a heatpipe solar receiver (HPSR) with thermal energy storage (TES) are presented. The HPSR features a 15-25 kWe Stirling engine power conversion system at the focal point of a parabolic dish concentrator operating at 827 C. The system collects and retrieves solar heat with sodium pipes and stores the heat in NaF-MgF2 latent heat storage material. The trials were run with a single full scale heatpipe, three full scale TES containers, and an air-cooled heat extraction coil to replace the Stirling engine heat exchanger. Charging and discharging, constant temperature operation, mixed mode operation, thermal inertial, etc. were studied. The heatpipe performance was verified, as were the thermal energy storage and discharge rates and isothermal discharges.

In manufacturing parts by molding method, temperature uniformity of the mold holds a very crucial aspect for the quality of the parts. Studies have been carried out in searching for effective method in controlling the mold temperature. Using of heatpipe is one of the many effective ways to control the temperature of the molding area to the right uniform level. Recently, there has been the development of oscillating heatpipe and its application is very promising. The semi-empirical correlation for closed-loop oscillating heatpipe (CLOHP) with the STD of ±30% was used in design of CLOHP in this study. By placing CLOHP in the copper plate at some distance from the plate surface and allow CLOHP to heat the plate up to the set surface temperature, the temperature of the plate was recorded. It is found that CLOHP can be effectively used as a heat source to transfer heat to copper plate with excellent temperature distribution. The STDs of heat rate of all experiments are well in the range of ±30% of the correlation used.

Full Text Available A hybrid photovoltaic solar assisted loop heatpipe/heat pump (PV-SALHP/HP water heater system has been developed and numerically studied. The system is the combination of loop heatpipe (LHP mode and heat pump (HP mode, and the two modes can be run separately or compositely according to the weather conditions. The performances of independent heat pump (HP mode and hybrid loop heatpipe/heat pump (LHP/HP mode were simulated and compared. Simulation results showed that on typical sunny days in spring or autumn, using LHP/HP mode could save 40.6% power consumption than HP mode. In addition, the optimal switchover from LHP mode to HP mode was analyzed in different weather conditions for energy saving and the all-year round operating performances of the system were also simulated. The simulation results showed that hybrid LHP/HP mode should be utilized to save electricity on sunny days from March to November and the system can rely on LHP mode alone without any power consumption in July and August. When solar radiation and ambient temperature are low in winter, HP mode should be used

Full Text Available The authors have investigated a LED lamp cooling system that operates on a heatpipe basis. The paper describes the experimental stand, methods and results of the tests carried out for the different positions of the lamp at energy consumption of 196 W. It is shown that the considered cooling system ensures proper temperature of LEDs.

Full Text Available A three-dimensional model was developed to simulate the heat transfer rate on a heatpipe in a transient condition. This article presents the details of a calculation domain consisting of a wall, a wick, and a vapor core. The governing equation based on the shape of the pipe was numerically simulated using the finite element method. The developed three-dimensional model attempted to predict the transient temperature, the velocity, and the heat transfer rate profiles at any domain. The values obtained from the model calculation were then compared with the actual results from the experiments. The experiment showed that the time required to attain a steady state (where transient temperature is constant was reasonably consistent with the model. The working fluid r134a (tetrafluoroethane was the quickest to reach the steady state and transferred the greatest amount of heat.

Waste heat recovery through thermoelectric generators is a promising way to improve energy conversion efficiency. This paper proposes a type of heatpipe assisted thermoelectric generator (HP-TEG) system. The expandable evaporator and condenser surface of the heatpipe facilitates the intensive assembly of thermoelectric (TE) modules to compose a compact device. Compared with a conventional layer structure thermoelectric generator, this system is feasible for the installment of more TE couples, thus increasing power output. To investigate the performance of the HP-TEG and the optimal number of TE couples, a theoretical model was presented and verified by experiment results. Further theoretical analysis results showed the performance of the HP-TEG could be further improved by optimizing the parameters, including the inlet air temperature, the thermal resistance of the heating section, and thermal resistance of the cooling structure. Moreover, applying a proper number of TE couples is important to acquire the best power output performance.

In the present work, experimental and theoretical investigations have been conducted on a copper/water wire plate micro heatpipe (MHP). The experimental results show that its effective thermal conductivity is improved by a factor 1.3 as compared to the empty MHP array. A numerical model is used to predict the fluid distribution along the MHP axis, the temperature field and the maximum heat flux corresponding to the MHP capillary limit. The 1D, steady-state hydrodynamic model is based on the conservation equations for the liquid and vapour phases. The wall temperatures are calculated from the thermal resistance network of the wall and the liquid film. A good agreement between the theoretical and experimental data is achieved. The effect of various parameters - contact angle, fluid type, corner angle, fill charge - is theoretically investigated. (authors)

Who does not know that? During the inspection of the building one enters the actually unheated cellar. One already begins with sweating. However, the old boiler is not guilty of the too high temperatures in the basement. Also the armatures and pipes delivering the heat distribution frequently dispense their energy to the environment, long before thermal heat and hot drinking warm water reach their ultimate target position.

In this experiment,a four-turn oscillating heatpipe(OHP)is made of copper tube with an inner diameter of 1.3mm,and an outer diameter of 2.5mm.A series of experiments are performed to investigate the startup characteristics of OHP,and the effects of different working fluids(FS-39E microcapsule fluid,pure water,ethanol),different liquid filling rates(40%-80%)on the heat transport capability of OHP in vertical bottom heat mode.The results show that the startup of OHP is relative with liquid filling rate,thermal driving force and working fluid;and experiences different flow patterns with the increase of heat load.The best concentration of FS-39E microcapsule fluid is 1wt%.While FS-39E microcapsule fluid is used as the working fluid,compared with pure water and ethanol,the OHP has a broader working scope;when the liquid filling rate is relatively high,the OHP shows a better performance on the startup and heat transport capability.

In this experiment, s four-turn oscillating heatpipe (OHP) is made of copper tube with an inner diameter of 1.3 mm, and an outer diameter of 2.5 mm. A series of experiments are performed to investigate the startup characteristics of OHP, and the effects of different working fluids (FS-39E microcapsule fluid, pure water, ethanol), different liquid filling rates (40%-80%) on the heat transport capability of OHP in vertical bottom heat mode. The results show that the startup of OHP is relative with liquid filling rate, thermal driving force and working fluid; and experiences different flow patterns with the increase of heat load. The best concentration of FS-39E microcapsule fluid is 1 wt%. While FS-39E microcapsule fluid is used as the working fluid, compared with pure water and ethanol, the OHP has a broader working scope; when the liquid filling rate is relatively high, the OHP shows a better performance on the startup and heat transport capability.

Full Text Available In this paper, a numerical simulation of heatpipeheat exchanger (HPHE is computed by using CFD solver program i.e. AcuSolve. Two idealized model of HPHE are created with different variant of entry’s dimension set to be case 1 and case 2. The geometry of HPHE is designed in SolidWorks and imported to AcuSolve to simulate the fluid flow numerically. The design of HPHE is the key to provide a heat exchanger system to work proficient as expected. Finally, the result is used to optimize and improving heat recovery systems of the increasing demand for energy efficiency in industry.

A high temperature superconducting (HTS) current lead test facility using heatpipe thermal intercepts is under development at the Superconducting Technology Center at Los Alamos National Laboratory. The facility can be configured for tests at currents up to 1,000 A. Mechanical cryocoolers provide refrigeration to the leads. Electrical isolation is maintained by intercepting thermal energy from the leads through cryogenic heatpipes. HST lead warm end temperature is variable from 65 K to over 90 K by controlling heatpipe evaporator temperature. Cold end temperature is variable up to 30 K. Performance predictions in terms of heatpipe evaporator temperature as a function of lead current are presented for the initial facility configuration, which supports testing up to 200 A. Measurements are to include temperature and voltage gradient in the conventional and HTS lead sections, temperature and heat transfer rate in the heatpipes. as well as optimum and off-optimum performance of the conventional lead sections.

This paper presents a feasibility study to improve thermal loading of existing radioactive material packages by using heatpipes. The concept could be used to channel heat in certain directions and dissipate to the environment. The concept is applied to a drum type package because the drum type packages are stored and transported in an upright position. This orientation is suitable for heatpipe operation that could facilitate the heatpipe implementation in the existing well proven package designs or in new designs where thermal loading is high. In this position, heatpipes utilize gravity very effectively to enhance heat flow in the upward direction Heatpipes have extremely high effective thermal conductivity that is several magnitudes higher than the most heat conducting metals. In addition, heatpipes are highly unidirectional so that the effective conductivity for heat transfer in the reverse direction is greatly reduced. The concept is applied to the 9977 package that is currently going through the DOE certification review. The paper presents computer simulations using typical off-the-shelf heatpipe available configurations and performance data for the 9977 package. A path forward is outlined for implementing the concepts for further study and prototype testing.

A series of 16 Mo-44.5%Re alloy/sodium heatpipes will be experimentally tested to examine heatpipe aging. To support this evaluation, an environmental test chamber and a number of auxiliary subsystems are required. These subsystems include radio frequency (RF) power supplies/inductive coils, recirculation water coolant loops, and chamber gas conditioning. The heatpipes will be grouped, based on like power and gas mixture requirements, into three clusters of five units each, configured in a pentagonal arrangement. The highest powered heatpipe will be tested separately. Test chamber atmospheric purity is targeted at test hardware, providing warning indicators followed by automatic shutdown should potentially damaging conditions develop. During hardware construction, a number of checkout tests.many making use of stainless steel prototype heatpipes that are already fabricated.will be required to verify operation.

Corrosion damages of pipes in district heating systems can occur both external and internal. The aim with this work has been to clarify external corrosion damages of pipes, and try to correlate the damages to the corrosivity of different soils and waters. For the analysis the Swedish District Heating Association's district heating system statistics has been used. The district heating system statistics shows that the cost for corrosion damages is high, and pipes older than 20 years have increased risk for corrosion. The knowledge about corrosion concerning steel poles and water pipes in soils can not be applied to external corrosion of steel pipes in district heating systems. The corrosion rate of steel poles in soils is low. The corrosion of steel pipes in district heating systems can locally give high rates, up to 0,5 mm/year. The mechanism for this type of corrosion is different compared to the corrosion mechanism of poles in soils. The temperature is higher and aggressive water, with road-salt and chloride content, falls in drops on the steel pipe, and impurities evaporate on the steel surface. These factors increase the corrosion rate. If the material thickness is 5 mm, fracture can occur in the pipe within ten years. The number of copper pipe corrosion damage is limited. The most determining corrosion factors of copper pipes are pH-value and impurities as chloride and sulphate in the water. Stainless steel pipes of type 304 can not be used in soils due to the risk of local corrosion. Higher alloyed stainless steels, with molybdenum and higher chromium content should be used. It is concluded that failures can occur due to external corrosion of steel pipes. This failure is expensive and can lead to human damage. One way to eliminate failures of steel pipes is to carry out risk analysis.

A computer program for numerical solution of differential equations that describe heatpipes with graded-porosity fibrous wicks is discussed. A mathematical problem is provided with a summary of the input and output steps used to solve it. The program is also applied to the analysis of a typical heatpipe.

This research aims at modeling and simulating the effects of nanofluids on cylindrical heatpipes thermal performance using the ANSYS-FLUENT CFD commercial software. The heatpipe outer wall temperature distribution, thermal resistance, liquid pressure and axial velocity in presence of suspended ...

An analysis is presented of experimental records obtained from a buried pipe grid of a heat pump , operated over a full heating season. The purpose of the analysis is to compare actual pipe performance with theory over a long period of time, thereby judging the applicability of the theory for practical use and to indicate the suitability of simplified design methods. (Author)

Differently designed heat-pipe evacuated tubular collectors have been investigated theoretically and experimentally. The theoretical work has included development of two TRNSYS [1] simulation models for heat-pipe evacuated tubular collectors utilizing solar radiation from all directions. One model...

National Aeronautics and Space Administration — This SBIR project aims to develop a lightweight, highly thermally and electrically conductive heatpipe plate for passive removal of the heat from the individual...

National Aeronautics and Space Administration — Loop HeatPipe (LHP) is a high performance heat transport device using capillary forces to circulate the working fluid in a closed loop. Conventional LHPs usually...

This paper presents the fabrication and application of a micro-scale hybrid wicking structure in a flat polymer-based heatpipeheat spreader, which improves the heat transfer performance under high adverse acceleration. The hybrid wicking structure which enhances evaporation and condensation heat transfer under adverse acceleration consists of 100 µm high, 200 µm wide square electroplated copper micro-pillars with 31 µm wide grooves for liquid flow and a woven copper mesh with 51 µm diameter wires and 76 µm spacing. The interior vapor chamber of the heatpipeheat spreader was 30×30×1.0 mm3. The casing of the heat spreader is a 100 µm thick liquid crystal polymer which contains a two-dimensional array of copper-filled vias to reduce the overall thermal resistance. The device performance was assessed under 0-10 g acceleration with 20, 30 and 40 W power input on an evaporator area of 8×8 mm2. The effective thermal conductivity of the device was determined to range from 1653 W (m K)-1 at 0 g to 541 W (m K)-1 at 10 g using finite element analysis in conjunction with a copper reference sample. In all cases, the effective thermal conductivity remained higher than that of the copper reference sample. This work illustrates the possibility of fabricating flexible, polymer-based heatpipeheat spreaders compatible with standardized printed circuit board technologies that are capable of efficiently extracting heat at relatively high dynamic acceleration levels.

In a Stirling radioisotope system, heat must continually be removed from the General Purpose Heat Source (GPHS) modules to maintain the modules and surrounding insulation at acceptable temperatures. Normally, the Stirling convertor provides this cooling. If the converter stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS, and also ending the mission. An alkali-metal Variable Conductance HeatPipe (VCHP) has been designed to allow multiple stops and restarts of the Stirling convertor in an Advanced Stirling Radioisotope Generator (ASRG). When the Stirling convertor is turned off, the VCHP will activate when the temperatures rises 30 C above the setpoint temperature. A prototype VCHP with sodium as the working fluid was fabricated and tested in both gravity aided and against gravity conditions for a nominal heater head temperature of 790 C. The results show very good agreement with the predictions and validate the model. The gas front was located at the exit of the reservoir when heater head temperature was 790 C while cooling was ON, simulating an operating Advanced Stirling Converter (ASC). When cooling stopped, the temperature increased by 30 C, allowing the gas front to move past the radiator, which transferred the heat to the case. After resuming the cooling flow, the front returned at the initial location turning OFF the VCHP. The against gravity working conditions showed a colder reservoir and faster transients.

The four miniature heatpipes filled with DI water and SiO2-water nanofluids containing different volume concentrations (0.2%, 0.6% and 1.0%) are experimentally measured on the condition of air and water cooling. The wall temperature and the thermal resistance are investigated for three inclination angles. At the same of inlet heat water temperature in the heat system, it is observed that the total wall temperatures on the evaporator section are almost retaining constant by air cooling and the wall temperatures at the front end of the evaporator section are slightly reduced by water cooling. However, the wall temperatures at the condenser section using SiO2-water nanofluids are all higher than that for DI water on the two cooling conditions. As compared with the heatpipe using DI water, the decreasing of the thermal resistance in heatpipe using nanofluids is about 43.10%-74.46% by air cooling and 51.43%-72.22% by water cooling. These indicate that the utilization of SiO2-water nanofluids as working fluids enhances the performance of the miniature heatpipe. When the four miniature heatpipes are cut to examine at the end of the experiment, a thin coating on the surface of the screen mesh of the heatpipe using SiO2-water nanofluids is found. This may be one reason for reinforcing the heat transfer performance of the miniature heatpipe.

Full Text Available One of the options on how to remove waste heat from electronic components is using loop heatpipe. The loop heatpipe (LHP is a two-phase device with high effective thermal conductivity that utilizes change phase to transport heat. It was invented in Russia in the early 1980’s. The main parts of LHP are an evaporator, a condenser, a compensation chamber and a vapor and liquid lines. Only the evaporator and part of the compensation chamber are equipped with a wick structure. Inside loop heatpipe is working fluid. As a working fluid can be used distilled water, acetone, ammonia, methanol etc. Amount of filling is important for the operation and performance of LHP. This work deals with the design of loop heatpipe and impact of filling ratio of working fluid to remove waste heat from insulated gate bipolar transistor (IGBT.

The experimental study results of the influence of porous metal fiber structures on the intensity of two-phase heat transfer of water and acetone boiling on porous surfaces in conditions of free movement and capillary transport of liquids are presented in the article. The experiments were realized using specially designed experimental installation simulated the operating conditions of heatpipes and thermosyphons. Such conditions are typical for two-phase heat transfer devices – heatpipes an...

Improvement of the air conditioning system performance by using the heatpipe for cooling air before entering the condenser is presented. In the experiment, the heatpipe is fabricated from the straight copper tube with the diameter and length of 10, 600 mm, respectively. The arrangements of the heatpipe sets are arranged in the staggered layout with the tube rows of 1, 2, 3. R134a refrigerant is used as working fluid in the heatpipe set for this present study. By comparing with a conventional air conditioning system, the air conditioning system with three rows of heatpipe gives the highest COP and EER with increasing of 6.4%, 17.5%, respectively. On the global warming and environment problems, the results of this study are expected to lead to guidelines that will allow the improved performance of the air conditioning systems which reduce its energy consumption.

If micro heatpipeheat transfers, the inside working fluid goes through a biphasic state. The flow of the liquid and the vapor thereof by the capillary beds of frittered copper and the layer of capillary polysynthetic material and migration of vapors liquid from the end, takes the heat flow towards the end where a transfer of heat may occur only if there is a difference in temperature between the end of a flat micro heatpipe that gives the acquirer heat and heat flux. The porosity of the material is total pore of the total material volume. In the analysis of heat and mass transfer through porous media, both convective and conductive transfer forms can not be separated, because of the surfaces in contact between the two capillar layers. It had been studied the dependence of the rate of flow of liquid through the frittered porous media, and Reynolds polysynthetic. It tracks changes in the Reynolds number based on the interior capillary porosity. They traced in Mathcad [1] the graphs for changing the Reynolds number of capillary pressure by capillary porosity.

Above-boiling temperature conditions, as encountered, forexample, in geothermal reservoirs and in geologic repositories for thestorage of heat-producing nuclear wastes, may give rise to stronglyaltered liquid and gas flow processes in porous subsurface environments.The magnitude of such flow perturbation is extremely hard to measure inthe field. We therefore propose a simple temperature-profile method thatuses high-resolution temperature data for deriving such information. Theenergy that is transmitted with the vapor and water flow creates a nearlyisothermal zone maintained at about the boiling temperature, referred toas a heatpipe. Characteristic features of measured temperature profiles,such as the differences in the gradients inside and outside of the heatpipe regions, are used to derive the approximate magnitude of the liquidand gas fluxes in the subsurface, for both steady-state and transientconditions.

Loop heatpipes (LHPs) are heat transfer devices whose operating principle is based on the evaporation/condensation of a working fluid, and which use the capillary pumping forces to ensure the fluid circulation. Their major advantages as compared to heatpipes are an ability to operate against gravity and a greater maximum heat transport capability. In this paper, a literature review is carried out in order to investigate how various parameters affect the LHP operational characteristics. This review is based on the most recent published experimental and theoretical studies. After a reminder of the LHP operating principle and thermodynamic cycle, their operating limits are described. The LHP thermal resistance and maximum heat transfer capability are affected by the choice of the working fluid, the fill charge ratio, the porous wick geometry and thermal properties, the sink and ambient temperature levels, the design of the evaporator and compensation chamber, the elevation and tilt, the presence of non-condensable gases, the pressure drops of the fluid along the loop. The overall objective for this paper is to point the state-of-the-art for the related technology for future design and applications, where the constraints related to the LHPs are detailed and discussed. (author) [French] Les boucles diphasiques a pompage capillaire sont des systemes dont le principe de fonctionnement est base sur l'evaporation/condensation d'un fluide et qui utilisent les forces de capillarite pour faire circuler le fluide dans la boucle. En comparaison des caloducs, les principaux avantages des boucles diphasiques a pompage capillaire sont une aptitude a vaincre les forces de gravite, lorsque le systeme est en position defavorable, et une puissance maximale transferable superieure. La presente etude bibliographique, basee sur les travaux experimentaux et theoriques les plus recents, a pour but est de comprendre comment differents parametres influencent le comportement de la

This paper presents some experimental results of an extensive research on a novel oscillating heatpipe. The heatpipe is formed of three interconnected columns as different from the pulsating heatpipe designs. The dimensions of the heatpipe considered in this study are large enough to neglect the effect of capillary forces. Thus, the self-oscillation of the system is driven by the gravitational force and the phase lag between the evaporation and condensation processes. The overall heat transfer coefficient is found to be approximately constant irrespective of heat load for the experimental cases considered. The results are also compared with the previously published data by other investigators for water as the working fluid and for the same heat input range. The experimental data for the time variation of the liquid column heights and the vapor pressure are correlated algebraically, convenient for practical uses.

Based on the heat transfer characteristics of absorber plate and the heat transfer effectiveness-number of heat transfer unit method of heat exchanger, a new theoretical method of analyzing the thermal performance of heatpipe flat plate solar collector with cross flow heat exchanger has been put forward and validated by comparisons with the experimental and numerical results in pre-existing literature. The proposed theoretical method can be used to analyze and discuss the influence of relevant parameters on the thermal performance of heatpipe flat plate solar collector.

Compact fission power systems are under consideration for use in long duration space exploration missions. Power demands on the order of 500 W, to 5 kW, will be required for up to 15 years of continuous service. One such small reactor design consists of a fast spectrum reactor cooled with an array of in-core alkali metal heatpipes coupled to thermoelectric or Stirling power conversion systems. Heatpipes advantageous attributes include a simplistic design, lack of moving parts, and well understood behavior. Concerns over reactor transients induced by heatpipe instability as a function of extreme thermal transients require experimental investigations. One particular concern is rapid cooling of the heatpipe condenser that would propagate to cool the evaporator. Rapid cooling of the reactor core beyond acceptable design limits could possibly induce unintended reactor control issues. This paper discusses a series of experimental demonstrations where a heatpipe operating at near prototypic conditions experienced rapid cooling of the condenser. The condenser section of a stainless steel sodium heatpipe was enclosed within a heat exchanger. The heatpipe - heat exchanger assembly was housed within a vacuum chamber held at a pressure of 50 Torr of helium. The heatpipe was brought to steady state operating conditions using graphite resistance heaters then cooled by a high flow of gaseous nitrogen through the heat exchanger. Subsequent thermal transient behavior was characterized by performing an energy balance using temperature, pressure and flow rate data obtained throughout the tests. Results indicate the degree of temperature change that results from a rapid cooling scenario will not significantly influence thermal stability of an operating heatpipe, even under extreme condenser cooling conditions.

Thermal-to-electrical energy conversion was demonstrated using an oscillating heatpipe (OHP) filled with ferrofluid and equipped with an annular-type solenoid. The OHP was subjected to a 100 °C axial temperature difference allowing the ferrofluid to passively oscillate through the solenoid, thus accomplishing electromagnetic induction. The measured solenoid voltage consisted of aperiodic pulses with dominant frequencies between 2 and 5 Hz and peak-to-peak amplitudes approaching 1 mV. Despite exposure to the thermal and phase change cycling within the OHP, nanoparticle morphologies and magnetic properties of the ferrofluid remained intact. This energy harvesting method allows for combined thermal management and in-situ power generation.

The design and testing of a heatpipe for spacecraft application is presented. The application in mind calls for heat loads up to 20 watts, a set-point temperature of 294K, and a sink that varies from -220K to nearly as high as the set-point. The overall heatpipe length is 137 cm. Two basically different mechanisms of achieving variable conductance in the pipe by vapor-flow throttling were studied. In one, the thermal resistance between the heat source and sink is due to a saturation-temperature drop corresponding to the vapor-pressure drop developed across the valve. In the other, the pressure difference across the valve induces capillary groove and wick dry out in an evaporation region, and thus results in an increased thermal resistance. This mechanism was selected for fabrication and testing. The pipe is a stainless-steel/methanol two-heat-pipe system. Results are presented and discussed. Engineering drawings and specifications of the pipe are shown.

The MLHP Thermal Management System consists of a loop heatpipe (LHP) with multiple evaporators and condensers, thermal electrical coolers, and deployable radiators coated with variable emittance coatings (VECs). All components are miniaturized. It retains all the performance characteristics of state-of-the-art LHPs and offers additional advantages to enhance the functionality, versatility, and reliability of the system, including flexible locations of instruments and radiators, a single interface temperature for multiple instruments, cooling the on instruments and warming the off instruments simultaneously, improving. start-up success, maintaining a constant LHP operating temperature over a wide range of instrument powers, effecting automatic thermal switching and thermal diode actions, and reducing supplemental heater powers. It can fully achieve low mass, low power and compactness necessary for future small spacecraft. Potential applications of the MLHP thermal technology for future missions include: 1) Magnetospheric Constellation; 2) Solar Sentinels; 3) Mars Science Laboratory; 4) Mars Scouts; 5) Mars Telecom Orbiter; 6) Space Interferometry Mission; 7) Laser Interferometer Space Antenna; 8) Jupiter Icy Moon Orbiter; 9) Terrestrial Planet Finder; 10) Single Aperture Far-Infrared Observatory, and 11) Exploration Missions. The MLHP Thermal Management System combines the operating features of a variable conductance heatpipe, a thermal switch, a thermal diode, and a state-of-the-art LHP into a single integrated thermal system. It offers many advantages over conventional thermal control techniques, and can be a technology enabler for future space missions. Successful flight validation will bring the benefits of MLHP technology to the small satellite arena and will have cross-cutting applications to both Space Science and Earth Science Enterprises.

Since the operation period of nuclear power plants has increased, the degradation of buried pipes gradually increases and recently it seems to be one of the emerging issues. Maintenance on buried pipes needs high quality of management system because outer surface of buried pipe contacts the various soils but inner surface reacts with various electrolytes of fluid. In the USA, USNRC and EPRI have tried to manage the degradation of buried pipes. However, there is little knowledge about the inspection procedure, test and manage program in the domestic nuclear power plants. This paper focuses on the development and build-up of real-time monitoring and control system of buried pipes. Pipes to be tested are tape-coated carbon steel pipe for primary component cooling water system, asphalt-coated cast iron pipe for fire protection system, and pre-stressed concrete cylinder pipe for sea water cooling system. A control system for cathodic protection was installed on each test pipe which has been monitored and controlled. For the calculation of protection range and optimization, computer simulation was performed using COMSOL Multiphysics (Altsoft co.)

The work presented here focuses on heat transfer augmentation by means of divergent-convergent spring turbulator (the enhancement device). Aim of the present work is to find such an optimum pitch at which the augmentation in heat transfer is maximum and the amount of power consumption is minimum, so that an economic design can be created with maximum thermal efficiency. So, the concept of pitch variation is introduced, which is defined as the horizontal distance between two consecutive turbulators. It describes that, the lesser is the pitch the more number of turbulators that can be inserted in inner pipe of double pipeheat exchanger, hence more will be the friction factor. This physics increases convective ability of the heat transfer process from the surface of inner pipe. There is a certain limit to which a pitch can be decreased, lesser the pitch the more the pressure drop and friction factor and hence the more will be the pumping power requirement to maintain a desired mass flow rate of hot water. Analysis of thermal factors such as Nusselts number, friction factor, with different pitches of divergent convergent spring turbulators of circular cross-section 15, 10, and 5 cm at Reynolds's number ranging between 9000 < Re < 40,000 is done graphically.

ATLAS Laser Thermal Control System (LTCS) thermal vacuum testing where the condenser-radiator was placed in a vertical position, it was found that the loop heatpipe (LHP) reservoir required much more control heater power than the analytical model had predicted. The required control heater power was also higher than the liquid subcooling entering the reservoir using the measured temperatures and the calculated mass flow rate based on steady state LHP operation. This presentation describes the investigation of the LHP behaviors under a gravity assist mode with a very cold radiator sink temperature and a large thermal mass attached to the evaporator. It is concluded that gravity caused the cold liquid to drop from the condenser-radiator to the reservoir, resulting in a rapid decrease of the reservoir temperature. When the reservoir temperature was increasing, a reverse flow occurred in the liquid line, carrying warm liquid to the condenser-radiator. Both events consumed the reservoir control heater power. The fall and rise of the reservoir temperature also caused the net heat input to the evaporator to vary due to the release and storage of the sensible heat of the thermal mass. The combination of these effects led to a persistent reservoir temperature oscillation and a repeated influx of cold liquid from the condenser. This was the root cause of the extraordinary high control heater power requirement in the LTCS TV test. Without gravity assist, such a persistent temperature oscillation will not be present.

Laminar air flow in a 90° bend has been studied numerically to investigate convective heat transfer, which is of practical relevance to electronic systems and refrigeration piping layout. CFD simulations are performed for Reynolds number in the range 200 to 1000 at different bend radius ratios (5, 10 and 20). The heat transfer characteristics are found to be enhanced in the curved pipe compared to a straight pipe, which are subjected to the same flow rate. The curvature and buoyancy effectively increase heat transfer in viscous laminar flows. The correlation between the flow structure and the heat transfer is found to be strong.

Plate tectonics is a unique feature of Earth, and it plays a dominant role in transporting Earth's internally generated heat. It also governs the nature, shape, and the motion of the surface of Earth. The initiation of plate tectonics on Earth has been difficult to establish observationally, and modeling of the plate breaking process has not consistently accounted for the nature of the preplate tectonic Earth. We have performed numerical simulations of heat transport in the preplate tectonic Earth to understand the transition to plate tectonic behavior. This period of time is dominated by volcanic heat transport called the heatpipe mode of planetary cooling. These simulations of Earth's mantle include heat transport by melting and melt segregation (volcanism), Newtonian temperature-dependent viscosity, and internal heating. We show that when heatpipes are active, the lithosphere thickens and lithospheric isotherms are kept flat by the solidus. Both of these effects act to suppress plate tectonics. As volcanism wanes, conduction begins to control lithospheric thickness, and large slopes arise at the base of the lithosphere. This produces large lithospheric stress and focuses it on the thinner regions of the lithosphere resulting in plate breaking events.

According to heatpipe theory,capillary force is the only driving force for the circle of working fluid in heatpipe with porous wick.By developing a simulating circuit of liquid and vapor flow in heatpipe with porous wick,this paper presents a new driving mechanism which is from phase change of fluid.Furthermore,by analyzing transport process of working fluid between evaporation and condensation in terfaces,a mathematical model is developed to describe this driving mechanism.Besides,calculating examples are given for heatpipe with water as working fluid to predict its driving force and flow resis tance.By applying the model presented in the paper,thermal design and calculation for heatpipe with porous wick,especially for miniature heatpipe,can be made correctly,and phase change driving me chanism of working fluid can be explained,which thereby leads to a better understanding of heat transfer limitation of heatpipe with porous wick.

Stresses and deformation states of pipe bending are investigated under loading or unloading with various pipe materials, size, bending radius and deformation temperature. A theorem of springback of large diameter pipe bending is presented. The experiments are carried out with pipe materials of 20, 10CrMo910 and 12Cr1MoV steel. Results of computations are in good agreement with experiments.

Thermal energy storage systems as an integral part of concentrated solar power plants improve the performance of the system by mitigating the mismatch between the energy supply and the energy demand. Using a phase change material (PCM) to store energy increases the energy density, hence, reduces the size and cost of the system. However, the performance is limited by the low thermal conductivity of the PCM, which decreases the heat transfer rate between the heat source and PCM, which therefore prolongs the melting, or solidification process, and results in overheating the interface wall. To address this issue, heatpipes are embedded in the PCM to enhance the heat transfer from the receiver to the PCM, and from the PCM to the heat sink during charging and discharging processes, respectively. In the current study, the thermal-fluid phenomenon inside a heatpipe was investigated. The heatpipe network is specifically configured to be implemented in a thermal energy storage unit for a concentrated solar power system. The configuration allows for simultaneous power generation and energy storage for later use. The network is composed of a main heatpipe and an array of secondary heatpipes. The primary heatpipe has a disk-shaped evaporator and a disk-shaped condenser, which are connected via an adiabatic section. The secondary heatpipes are attached to the condenser of the primary heatpipe and they are surrounded by PCM. The other side of the condenser is connected to a heat engine and serves as its heat acceptor. The applied thermal energy to the disk-shaped evaporator changes the phase of working fluid in the wick structure from liquid to vapor. The vapor pressure drives it through the adiabatic section to the condenser where the vapor condenses and releases its heat to a heat engine. It should be noted that the condensed working fluid is returned to the evaporator by the capillary forces of the wick. The extra heat is then delivered to the phase change material

Full Text Available Thermal performance of a cylindrical heatpipe is investigated numerically. Three different types of water based nanofluids, namely, Al2O3 + Water, Diamond + Water, and Multi-Wall Carbon Nano tube (MWCNT + Water, have been used. The influence of using the simple nanofluids and MWCNT nanofluid on the heatpipe characteristics such as liquid velocity, pressure profile, temperature profile, thermal resistance, and heat transfer coefficient of heatpipe has been studied. A new correlation developed by Bakhshan and Saljooghi (2014 for viscosity of nanofluids has been implemented. The results show, a good agreement with the available analytical and experimental data. Also the results show, that the MWCNT based nanofluid has lower thermal resistance, higher heat transfer coefficient, and lower temperature difference between evaporator and condenser sections, so it has good thermal specifications as a working fluid for use in heatpipes. The prepared code has capability for parametric studies also.

The purpose of this paper is to discuss concepts for using high temperature heatpipes to transport energy from a heat source to a thermophotovoltaic (TPV) converter. Within the converter, the condenser portion of each heatpipe acts as a photon radiator, providing a radiant flux to adjacent TPV cells, which in turn create electricity. Using heatpipes in this way could help to increase the power output and the power density of TPV systems. TPV systems with radiator temperatures in the range of 1,500 K are expected to produce as much as 3.6 W/cm{sup 3} of heat exchanger volume at an efficiency of 20% or greater. Four different arrangements of heatpipe-TPV energy converters are considered. Performance and sizing calculations for each of the concepts are presented. Finally, concerns with this concept and issues which remain to be considered are discussed.

A rack cooling system based on a large scale flat plate pulsating heatpipe is proposed. The heat generated from IT equipment in a closed rack is transferred by the rear door pulsating heatpipe to the chilled air passage and is avoided to release into the room. The influence of the start-up performance of the heatpipe, the load of the rack and the load dissipation to the temperature and the velocity distribution in the rack are discussed. It is found that the temperature would be lower and the temperature distribution would be more uniform in the rack when the pulsating heatpipe is in operation. Also, the effect of rack electricity load on temperature distribution is analyzed. It is indicated that higher velocity of chilled air will improve heat transfer of the rack.

Full Text Available The three dimensional mixed convection heat transfer in a electrically heated horizontal pipe conjugated to a thermal conduction through the entire solid thickness is investigated by taking into account the thermal dependence of the physical properties of the fluid and the outer heat losses. The model equations of continuity, momentum and energy are numerically solved by the finite volume method. The pipe thickness, the Prandtl and the Reynolds numbers are fixed while the Grashof number is varied from 104to107. The results obtained show that the dynamic and thermal fields for mixed convection are qualitatively and quantitatively different from those of forced convection, and the local Nusselt number at the interface solid-fluid is not uniform: it has considerable axial and azimuthally variations. The effect of physical variables of the fluid depending on temperature is significant, which justifies its inclusion. The heat transfer is quantified by the local and average Nusselt numbers. We found that the average Nusselt number of solid-fluid interface of the duct increases with the increase of Grashof number. We have equally found out that the heat transfer is improved thanks to the consideration of the thermo dependence of the physical properties. We have tried modelling the average Nusselt number as a function of Richardson number. With the parameters used, the heat transfer is quantified by the correlation: NuA=12.0753 Ri0.156

Full Text Available Abstract The effect of alumina nanoparticles on the heat transfer performance of an oscillating heatpipe (OHP was investigated experimentally. A binary mixture of ethylene glycol (EG and deionized water (50/50 by volume was used as the base fluid for the OHP. Four types of nanoparticles with shapes of platelet, blade, cylinder, and brick were studied, respectively. Experimental results show that the alumina nanoparticles added in the OHP significantly affect the heat transfer performance and it depends on the particle shape and volume fraction. When the OHP was charged with EG and cylinder-like alumina nanoparticles, the OHP can achieve the best heat transfer performance among four types of particles investigated herein. In addition, even though previous research found that these alumina nanofluids were not beneficial in laminar or turbulent flow mode, they can enhance the heat transfer performance of an OHP.

Many proposed space reactor designs employ heatpipes as a means of conveying heat. Previous researchers have been concerned with steady state operation, but the transient operation is of interest in space reactor applications due to the necessity of remote startup and shutdown. A model is being developed to study the dynamic behavior of high temperature heatpipes during startup, shutdown and normal operation under space environments. Model development and preliminary results for a hypothetical design of the system are presented.

The synergy between highly energy-efficient buildings and low-energy district heating (DH) systems is a promising concept for the optimal integration of energy-saving policies and energy supply systems based on renewable energy (RE). Network transmission and distribution heat loss is one of the key...... factors in the optimal design of low-energy DH systems. Various pipe configurations are considered in this paper: flexible pre-insulated twin pipes with symmetrical or asymmetrical insulation, double pipes, and triple pipes. These technologies represent potential energy-efficient and cost...... showed the influence of the soil temperature throughout the year. Finally, the article describes proposals for the optimal design of pipes for low-energy applications and presents methods for decreasing heat losses....

Full Text Available An experimental study of three different cross-sections (circular, semicircular and rectangular of micro heatpipes having same hydraulic diameter (D= 3mm is carried out at three different inclination angles (0°, 45°, 90° using water as the working fluid. Evaporator section of the pipe is heated by an electric heater and the condenser section is cooled by water circulation in an annular space between the condenser section and the water jacket. Temperatures at different locations of the pipe are measured using five calibrated K type thermocouples. Heat supply is varied using a voltage regulator which is measured by a precision ammeter and a voltmeter. It is found that thermal performance tends to deteriorate as the micro heatpipe is flattened. Thus among all cross-sections of the pipes circular cross-section exhibits the best thermal performance followed by semicircular and rectangular cross-sections. Moreover maximum heat transfer capability of the pipes also decreases with decreasing of its inclination angle. A correlation is developed using all the gathered data of the present study to predict the heat transfer coefficient of micro heatpipes of different cross-sections placed at different inclination angles.

Full Text Available This paper presents For Experimental and Exergy Analysis of a Double PipeHeat Exchanger for Parallel- flow Arrangement. The Double pipeheat exchanger is one of the Different types of heat exchangers. double-pipe exchanger because one fluid flows inside a pipe and the other fluid flows between that pipe and another pipe that surrounds the first.In a parallel flow, both the hot and cold fluids enter the Heatexchanger at same end andmove in same direction. The present work is taken up to carry experimental work and the exergy analysis based on second law analysis of a Double-PipeHeat Exchanger. In experimental set up hot water and cold water will be used working fluids. The inlet Hot water will be varied from 40 0C and 50 0C and cold water temperature will be varied from between 15 and 20 0C. It has been planned to find effects of the inlet condition of both working fluid flowing through the heat exchanger on the heat transfer characteristics, entropy generation, and Exergy loss. The Mathematical modelling of heat exchanger will based on the conservation equation of mass, energy and based on second law of thermodynamics to find entropy generation and exergy losses.

Full Text Available Heatpipes as cooling devices have a high potential. Their power to affect a variety of factors – the vapour pressure, the amount of media work etc. Itis therefore necessary to verify the calculated parameters also practically. To determine the performance of transmitted heatpipe is the best calorimetric method. When it is out of the flow and the temperature difference the cooling part of the heatpipe determines its transmitted power. The contribution is focused on comparison of two types of coolers. The first type is looped capillary cooler for the condenser section. The small diameter capillary is secured high coolant turbulence and hence heat dissipation. The second type is non-contact cooling, where cooling fluid washes direct heatpipe wall.

Full Text Available The fabrication and performance of wicks for flat heatpipe applications produced by sintering a filamentary nickel powder has been investigated. Tape casting was used as an intermediate step in the wick production process. Thermogravimetric analysis was used to study the burn-off of the organic binder used and to study the oxidation and reduction processes of the nickel. The wicks produced were flat, rectangular and intended for liquid transport in the upwards vertical direction. Rate-of-rise experiments using heptane were used to test the flow characteristics of the wicks. The wick porosities were measured using isopropanol. The heat transfer limitation constituted by the vapour static pressure and the capillary pressure was discussed. The influence on wick performance by using pore former in the manufacturing was studied. When Pcap/Psat > 1, the use of a pore former to increase the wick permeability will always improve the wick performance. When Pcap/Psat < 1, it was shown that if the effective pore radius and the permeability increase with an equal percentage the overall influence on the wick capacity is negative. A criterion for a successful pore former introduction is proposed and the concept of a pore former evaluation plot is presented.

Full Text Available The heat transfer coefficients and friction factors of a baffled shell and heatpipeheat exchanger with various inclination angles were determined experimentally; using methanol as working fluid and water as heat transport fluid were reported. Heatpipeheat exchanger reported in this investigation have inclination angles varied between 15o and 60o for different mass flow rates and temperature at the shell side of the heat exchanger. All the required parameters like outlet temperature of both hot and cold side of heat exchanger and mass flow rate of fluids were measured using an appropriate instrument. Different tests were performed from which condenser side heat transfer coefficient and friction factor were calculated. In all operating conditions it has been found that the heat transfer coefficient increases by increasing the mass flow rate and angle of inclination. The reduction in friction factor occurs when the Reynolds number is increased. The overall optimum experimental effectiveness of GABSHPHE has found to be 42% in all operating conditioning at ψ = 45o.

Full Text Available Problem statement: Currently, the heatpipe air-preheater has become importance equipment for energy recovery from industrial waste heat because of its low investment cost and high thermal conductivity. Approach: This purpose of the study was to design, construct and test the waste heat recovery by heatpipe air-preheater from the furnace in a hot brass forging process. The mathematical model was developed to predict heat transfer rate and applied to compute the heatpipe air-preheater in a hot brass forging process. The heatpipe air-preheater was designed, constructed and tested under medium temperature operating conditions with inlet hot gas ranging between 370-420°C using water as the working fluid with 50% filling by volume of evaporator length. Results: The experiment findings indicated that when the hot gas temperature increased, the heat transfer rate also increased. If the internal diameter increased, the heat transfer rate increased and when the tube arrangement changed from inline to staggered arrangement, the heat transfer rate increased. Conclusion/Recommendations: The heatpipe air-preheater can reduced the quantity of using gas in the furnace and achieve energy thrift effectively.

Oxygen dissolving in district heating water through district heatpipes and pipe joints made of plastic corrodes many small and medium-size district heating systems, resulting in heat cuts in the buildings connected to these systems. IN some cases, corrosion products have even circulated back to district heating power plants, thus hampering heat generation in the worst of cases. People residing in blocks of flats where some radiator components are made of plastic also face a similar problem, though on a smaller scale. A small and efficient electrochemical deoxidation cell has now been invented to eliminate this nuisance, which occurs particularly in cold winter weather. (orig.)

Oxygen dissolving in district heating water through district heatpipes and pipe joints made of plastic corrodes many small and medium-size district heating systems, resulting in heat cuts in the buildings connected to these systems. IN some cases, corrosion products have even circulated back to district heating power plants, thus hampering heat generation in the worst of cases. People residing in blocks of flats where some radiator components are made of plastic also face a similar problem, though on a smaller scale. A small and efficient electrochemical deoxidation cell has now been invented to eliminate this nuisance, which occurs particularly in cold winter weather. (orig.)

The issue of mold cooling is one, which presents a foundry with a dilemma. On the one hand; the use of air for cooling is safe and practical, however, it is not very effective and high cost. On the other hand, water-cooling can be very effective but it raises serious concerns about safety, especially with a metal such as magnesium. An alternative option that is being developed at McGill University uses heatpipe technology to carry out the cooling. The experimental program consisted of designing a permanent mold to produce AZ91E magnesium alloy and A356 aluminum alloy castings with shrinkage defects. Heatpipes were then used to reduce these defects. The heatpipes used in this work are novel and are patent pending. They are referred to as McGill HeatPipes. Computer modeling was used extensively in designing the mold and the heatpipes. Final designs for the mold and the heatpipes were chosen based on the modeling results. Laboratory tests of the heatpipe were performed before conducting the actual experimental plan. The laboratory testing results verified the excellent performance of the heatpipes as anticipated by the model. An industrial mold made of H13 tool steel was constructed to cast nonferrous alloys. The heatpipes were installed and initial testing and actual industrial trials were conducted. This is the first time where a McGill heatpipe was used in an industrial permanent mold casting process for nonferrous alloys. The effects of cooling using heatpipes on AZ91E and A356 were evaluated using computer modeling and experimental trials. Microstructural analyses were conducted to measure the secondary dendrite arm spacing, SDAS, and the grain size to evaluate the cooling effects on the castings. The modeling and the experimental results agreed quite well. The metallurgical differences between AZ91E and A356 were investigated using modeling and experimental results. Selected results from modeling, laboratory and industrial trials are presented. The

Test failures of heatpipes occur when the functional performance is unable to match the expected design limits or when the power applied to the heatpipe (in the form of heat) is distributed unevenly through the system, yielding a large thermal gradient. When a thermal gradient larger than expected is measured, it normally occurs in the evaporator or condenser sections of the pipe. Common causes include evaporator overheating, condenser dropout, noncondensable gas formation, surge and partial recovery of evaporator temperatures, masking of thermal profiles, and simple malfunctions due to leaks and mechanical failures or flaws. Examples of each of these phenomena are described along with corresponding failure analyses and corrective measures.

In order to evaluate the possibility to use heatpipes as efficient heat transfer devices in aircrafts, a study of their behaviour during strong accelerations is necessary. This study has been jointly carried out by the Laboratory of Thermal Studies of Poitiers (France) and Dassault Aviation company. It is based on a series of tests performed with an experimental apparatus that uses the centrifugal effect to simulate the acceleration fields submitted to the heatpipe. Un-priming - priming cycles have been performed under different power and acceleration levels and at various functioning temperatures in order to explore the behaviour of heatpipes: rate of un-priming and re-priming, functioning in blocked mode etc.. This preliminary study demonstrates the rapid re-priming of the tested heatpipes when submitted to favourable acceleration situations and the possibility to use them under thermosyphon conditions despite the brief unfavourable acceleration periods encountered. (J.S.)

Continuing efforts in large gains in heat-pipe performance are reported. It was found that gas-controlled variable-conductance heatpipes can perform reliably for long periods in space and effectively provide temperature stabilization for spacecraft electronics. A solution was formulated that allows the control gas to vent through arterial heat-pipe walls, thus eliminating the problem of arterial failure under load, due to trace impurities of noncondensable gas trapped in an arterial bubble during priming. This solution functions well in zero gravity. Another solution was found that allows priming at a much lower fluid charge. A heatpipe with high capacity, with close temperature control of the heat source and independent of large variations in sink temperature was fabricated.

The technology, dimensioning and performances of heatpipes are well known since several years. Micro-heatpipes occurred more recently with the miniaturization of systems to be cooled and the increase of surface heat fluxes to be dissipated. Publications concerning this topic are not much older than the 90`s. Using these papers, a bibliographic synthesis on micro-heatpipe performances, functioning and dimensioning is presented. Experimental studies demonstrate the efficiency of such systems but also their high sensitivity with respect to the capillary limit which leads to a progressive drying of the evaporator and a reduction of its thermal conductance. Theoretical studies are based on the same equations than heatpipes. More or less complex models have been proposed in the literature and a relatively simple model is presented in this paper. These studies have permitted to show the great influence of some parameters on micro-heatpipes functioning like: the pipe geometry, the fluid-wall contact angle, the level of pipes filling, and the bonding zone of the liquid film on the wall. (J.S.) 15 refs.

The traditional constant conductance heatpipes (CCHPs) currently used on most spacecraft run the risk of bursting the pipe when the working fluid is frozen and later thawed. One method to avoid pipe bursting is to use a gas-charged heatpipe (GCHP) that can sustain repeated freeze/thaw cycles. The construction of the GCHP is similar to that of the traditional CCHP except that a small amount of non-condensable gas (NCG) is introduced and a small length is added to the CCHP condenser to serve as the NCG reservoir. During the normal operation, the NCG is mostly confined to the reservoir, and the GCHP functions as a passive variable conductance heatpipe (VCHP). When the liquid begins to freeze in the condenser section, the NCG will expand to fill the central core of the heatpipe, and ice will be formed only in the grooves located on the inner surface of the heatpipe in a controlled fashion. The ice will not bridge the diameter of the heatpipe, thus avoiding the risk of pipe bursting during freeze/thaw cycles. A GCHP using ammonia as the working fluid was fabricated and then tested inside a thermal vacuum chamber. The GCHP demonstrated a heat transport capability of more than 200W at 298K as designed. Twenty-seven freeze/thaw cycles were conducted under various conditions where the evaporator temperature ranged from 163K to 253K and the condenser/reservoir temperatures ranged from 123K to 173K. In all tests, the GCHP restarted without any problem with heat loads between 10W and 100W. No performance degradation was noticed after 27 freeze/thaw cycles. The ability of the GCHP to sustain repeated freeze/thaw cycles was thus successfully demonstrated.

Two factors which incline nations toward the use of heat from nuclear reactors for industrial use are: 1) exhaustion of cheap fossil fuel resources, and 2) ecological problems associated both with extraction of fossil fuel from the earth and with its combustion. In addition to the usual problems that beset nuclear reactors, special problems associated with using heat from nuclear reactors in various industries are explored.

During the operation of a loop heatpipe (LHP), the viscous flow induces pressure drops in various elements of the loop. The total pressure drop is equal to the sum of pressure drops in vapor grooves, vapor line, condenser, liquid line and primary wick, and is sustained by menisci at liquid and vapor interfaces on the outer surface of the primary wick in the evaporator. The menisci will curve naturally so that the resulting capillary pressure matches the total pressure drop. In ground testing, an additional gravitational pressure head may be present and must be included in the total pressure drop when LHP components are placed in a non-planar configuration. Under gravity-neutral and anti-gravity conditions, the fluid circulation in the LHP is driven solely by the capillary force. With gravity assist, however, the flow circulation can be driven by the combination of capillary and gravitational forces, or by the gravitational force alone. For a gravity-assist LHP at a given elevation between the horizontal condenser and evaporator, there exists a threshold heat load below which the LHP operation is gravity driven and above which the LHP operation is capillary force and gravity co-driven. The gravitational pressure head can have profound effects on the LHP operation, and such effects depend on the elevation, evaporator heat load, and condenser sink temperature. This paper presents a theoretical study on LHP operations under gravity-neutral, anti-gravity, and gravity-assist modes using pressure diagrams to help understand the underlying physical processes. Effects of the condenser configuration on the gravitational pressure head and LHP operation are also discussed.

An experimental study was conducted to investigate the thermal performances of a new type of wire-bonded mesh screen flat heatpipe using water and nanofluid as working fluid to find better structure and the working fluid based on the present flat heatpipes. The influences of the kind of working fluid, mass concentration of nanofluid and operating pressure on the thermal performance of the heatpipe were investigated under the three steady operating pressures. It is found from the results that the thermal performance of wire-bonded mesh screen heatpipe are superior to that of wire-bonded flat heatpipe either using water or using nanofluid as working fluid; the thermal resistance of the former reduces distinctly and the maximum power increases obviously. Moreover, using nanofluid can significantly enhance the thermal performance of this heatpipe; enhanced ratios of the both heat transfer coefficient and maximum heat flux gradually increase with increasing the nanoparticle mass concentration in the nanofluid at the same operating pressure, peaking at the 1.0 wt%. Then, they will gradually reduce with further increase of mass concentration of nanofluid.

Modeling and simulation of a water-in-steel heatpipeheat recovery system is undertaken in this paper. The heat recovery system consists of a looped two-phase thermosyphon that receives heat from the stack of a gas turbine engine and delivers it to the generator of an NH{sub 3}-H{sub 2}O absorption chiller. Variations in the operating temperature as well as evaporator geometry are investigated, and the consequences on system effectiveness are studied. It is concluded that the model for the water-in-steel looped thermosyphon overcomes drawbacks of the water-in-copper thermosyphon, and that the steel system is simpler in design, lower in cost, and more competent in performance. (author)

In this study, effect of Al2O3 nanofluid on thermal performance of cylindrical heatpipe is investigated. An analytical model is employed to study the thermal performance of the heatpipe utilizing nanofluid and the predicted results are compared with the experimental results. A substantial change in the heatpipe thermal resistance, effective thermal conductivity and entropy generation of the heatpipe is observed when using Al2O3 nanofluid as a working fluid. It is found that entropy generation in the heatpipe system decreases when using a nanofluid due to the lower thermal resistance of the heatpipe which results in an improved thermal performance. It is shown that the proposed model is in reasonably good agreement with the experimental results and can be used as a fast technique to explore various features of thermal characteristics of the nanofluid based heatpipe.

A desirable feature of concentrated solar power (CSP) with integrated thermal energy storage (TES) unit is to provide electricity in a dispatchable manner during cloud transient and non-daylight hours. Latent heat thermal energy storage (LHTES) offers many advantages such as higher energy storage density, wider range of operating temperature and nearly isothermal heat transfer relative to sensible heat thermal energy storage (SHTES), which is the current standard for trough and tower CSP systems. Despite the advantages mentioned above, LHTES systems performance is often limited by low thermal conductivity of commonly used, low cost phase change materials (PCMs). Research and development of passive heat transfer devices, such as heatpipes (HPs) to enhance the heat transfer in the PCM has received considerable attention. Due to its high effective thermal conductivity, heatpipe can transport large amounts of heat with relatively small temperature difference. The objective of this research is to study the charging and discharging processes of heatpipe-assisted LHTES systems using computational fluid dynamics (CFD) and experimental testing to develop a method for more efficient energy storage system design. The results revealed that the heatpipe network configurations and the quantities of heatpipes integrated in a thermal energy storage system have a profound effect on the thermal response of the system. The optimal placement of heatpipes in the system can significantly enhance the thermal performance. It was also found that the inclusion of natural convection heat transfer in the CFD simulation of the system is necessary to have a realistic prediction of a latent heat thermal storage system performance. In addition, the effects of geometrical features and quantity of fins attached to the HPs have been studied.

Full Text Available An experimental investigation was conducted, both thermally and visually, on a three-dimensional flat-plate oscillating heatpipe (3D FP-OHP to characterize its performance under localized heat fluxes while operating in the bottom heating mode and charged with acetone at a filling ratio of 0.73. The cooling area was held constant and three heating areas of 20.16 cm2, 11.29 cm2, and 1.00 cm2 were investigated, respectively. It was found that as the heating area was reduced and higher heat fluxes were imposed, the thermal resistance increased and the amplitude of thermal oscillations in the evaporator increased and became more chaotic. Using neutron radiography, it was observed that fluid oscillations did not occur in outer channels located away from the region of local heating. Although the thermal resistance increased during localized heating, a maximum heat flux of 180 W/cm2 was achieved with the average evaporator temperature not exceeding 90∘C.

The development and application of Stirling engines for space power production requires concomitant development of an advanced heat rejection system. We are currently involved in the design, development, and testing of advanced ceramic fabric (ACF) water heatpipes for optimal heat rejection from the Stirling cycle without the use of hazardous working fluids such as mercury. Our testing to-date has been with a 200-{mu}m thick titanium heatpipe utilizing Nextel {trademark} fabric as both the outer structural component and as a wick. This heatpipe has been successfully started up from a frozen condition against a negative 4 degree tilt (i.e., fluid return to evaporator was against gravity), with 75 W heat input, in ambient air. In a horizontal orientation, up to 100 W heat input was tolerated without experiencing dryout. 7 refs., 5 figs., 2 tabs.

This report describes the recommissioning, upgrading, and maintaining of thirty low and five high temperature heatpipe life test rigs. This is an ongoing research effort, originally put together by NASA LeRC, continued by the Air Force. The 92 cm long 1.27 cm dia. spacecraft-type heatpipes have completed nearly 74,000 hours of life tests. They exhibit varying Delta Ts across the length and symptoms of gas accumulation. Life test status and temperature profile for each pipe are presented. The sodium and potassium pipes have undergone relatively less hours of testing (34,000 hours) only. These five pipes are exhibiting normal status. All the life tests will continue till failure and there will be updates of this report.

Crusts of the terrestrial planets other than Earth are dominated by mafic / ultramafic volcanics, with some contractional tectonics and minor extension. This description may also fit the early Earth. Therefore, a single process may have controlled early crustal development. Here we explore the hypothesis that heat-pipe cooling mode dominates early phases of terrestrial planet evolution. Volcanism is the hallmark of heat-pipe cooling: hot magma moves through the lithosphere in narrow channels, then is deposited and cools at the surface. A heat-pipe planet develops a thick, cold, downward-advecting lithosphere dominated by mafic/ultra-mafic flows. Contractional deformation occurs throughout the lithosphere as the surface is buried and forced toward smaller radii. Geologies of the Solar system's terrestrial planets are consistent with early heat-pipe cooling. Mercury's surface evolution is dominated by low-viscosity volcanism until ~4.1-4.0 Ga, with little activity other than global contraction since. Similar, younger features at Venus are commonly interpreted in terms of catastrophic resurfacing events with ~0.5 billion-year periodicity, but early support of high topography suggests a transition from heat-pipe to rigid-lid tectonics. Thick heat-pipe lithosphere may preserve the crustal dichotomy between Mars' northern and southern hemispheres, and explain the range in trace element abundances and isotopic compositions of Martian meteorites. At the Moon, global serial volcanism can explain refinement of ferroan anorthite rich rocks and coeval production of the "Mg-suite" rocks. The Moon's shape is out of hydrostatic equilibrium; it may represent a fossil preserved by thick early lithosphere. Active development of Jupiter's moon Io, which is warmed by tidal heating, is widely interpreted in terms of heat-pipe cooling. Given its potential ubiquity in the Solar system, heat-pipe cooling may be a universal process experienced by all terrestrial bodies of sufficient size.

Full Text Available Loop heatpipes (LHPs are used in many branches of industry, mainly for cooling of electrical elements and systems. The loop heatpipe is a vapour-liquid phase-change device that transfers heat from evaporator to condenser. One of the most important parts of the LHP is the porous wick structure. The wick structure provides capillary force to circulate the working fluid. To achieve good thermal performance of LHP, capillary wicks with high permeability and porosity and fine pore radius are expected. The aim of this work was to develop porous structures from copper and nickel powder with different grain sizes. For experiment copper powder with grain size of 50 and 100 μm and nickel powder with grain size of 10 and 25 μm were used. Analysis of these porous structures and LHP design are described in the paper. And the measurements’ influences of porous structures in LHP on heat removal from the insulated gate bipolar transistor (IGBT have been made.

The Laser Thermal Control System (LCTS) for the Advanced Topographic Laser Altimeter System (ATLAS) to be installed on NASA's Ice, Cloud, and Land Elevation Satellite (ICESat-2) consists of a constant conductance heatpipe and a loop heatpipe (LHP) with an associated radiator. During the recent thermal vacuum testing of the LTCS where the LHP condenser/radiator was placed in a vertical position above the evaporator and reservoir, it was found that the LHP reservoir control heater power requirement was much higher than the analytical model had predicted. Even with the control heater turned on continuously at its full power, the reservoir could not be maintained at its desired set point temperature. An investigation of the LHP behaviors found that the root cause of the problem was fluid flow and reservoir temperature oscillations, which led to persistent alternate forward and reversed flow along the liquid line and an imbalance between the vapor mass flow rate in the vapor line and liquid mass flow rate in the liquid line. The flow and temperature oscillations were caused by an interaction between gravity and reservoir heating, and were exacerbated by the large thermal mass of the instrument simulator which modulated the net heat load to the evaporator, and the vertical radiator/condenser which induced a variable gravitational pressure head. Furthermore, causes and effects of the contributing factors to flow and temperature oscillations intermingled.

It is proposed to develop a solar-to-gas heat exchanger for a Central Solar Receiver Power Plant. The concept employs heatpipes to transfer the concentrated solar flux to the gaseous working medium of a Brayton cycle conversion system. During early phases of the program, an open air cycle with recuperator and a turbine inlet temperature of 800/sup 0/C was selected as the optimum design. The predicted cycle efficiency is 33 percent and the overall solar-to-electric efficiency is 20 percent. Three potential receiver configurations were also identified during the initial phases of the program. Optimum heatpipe diameter is approximately 5 cm for all three receiver configurations, and typical lengths are 2 to 3 meters. The required number of heatpipes for a 10 MWe receiver ranges from 2000 to 8000. Heat transport requirements per pipe vary from 4 to 18 Kw. Several wick structures were developed and evaluated in subscale heatpipe tests using sodium as the working fluid. One full scale heatpipe (5 cm diameter by 183 cm long) was developed and tested with sodium as the working fluid.

Neutral beam injection heating is one of the main auxiliary heating methods in controllable nuclear fusion research. In the EAST neutral beam injector, a water flow calorimetry (WFC) system is applied to measure the heat load on the electrode system of the ion source and the heat loading components of the beamline. Due to the heat loss in the return water pipe, there are some measuring errors for the current WFC system. In this paper, the errors were measured experimentally and analyzed theoretically, which lay a basis for the exact calculation of beam power deposition distribution and neutralization efficiency. supported by the National Magnetic Confinement Fusion Science Program of China (No. 2013GB101001) and the International Science & Technology Cooperation Program of China (No. 2014DFG61950)

The piping systems in nuclear power plant are composed of various typed pipes such as straight pipe, elbow, branch and reducer etc. The elbow is connected from straight pipe to another pipes in order to establish the complicated piping system. Elbow is one of very important components considering management of wall thinning degradation. It is however applied by various loads such as system pressure, earthquake, postulated break loading and many transient loads, which provoke simply the internal pressure, bending and torsional stress. In this study, firstly pipes in the secondary system of the nuclear power plant are investigated in view of the ratio of radius to thickness. Next, a large number of finite element analysis considering the all typed dimensions of commercial pipe has been performed to find out the behavior of TES(Twice Elastic Slope) plastic load of elbows, which is based on evaluation of the structural safety factor. Finally performance based structural safety factor was investigated comparing with maximum allowable load by construction code.

National Aeronautics and Space Administration — This Small Business Innovative Research project by Advanced Cooling Technologies, Inc. (ACT) will develop an advanced high temperature heatpipe solar receiver that...

Differently designed heat-pipe evacuated tubular collectors have been investigated theoretically and experimentally. The theoretical work has included development of two TRNSYS [1] simulation models for heat-pipe evacuated tubular collectors utilizing solar radiation from all directions. One model...... coating on both sides. The input to the models is thus not a simple collector efficiency expression but the actual collector geometry. In this study, the TRNSYS models are validated with measurements for four differently designed heat-pipe evacuated tubular collectors. The collectors are produced...... cases, a good degree of similarity between measured and calculated results is found. With these validated models detailed parameter analyses and collector design optimization are now possible. Key words: Evacuated tubular collector, Heatpipe, Thermal performance, TRNSYS simulation....

National Aeronautics and Space Administration — The proposed program will develop titanium/water heatpipes suitable for Spacecraft Fission Power. NASA is examining small fission power reactors for future space...

Data on design features and operational experience of 40 hot water and steam district-heating networks with an overall heat capacity of 18,000 MWt have been collected, systematized, and analyzed. Piping networks located in Canada, Denmark, Finland, France, Italy, Japan, Netherlands, Sweden, USA, USSR, and West Germany have been analyzed and the data assembled. The data bank and analysis of the operational experience design features of hot water and steam district-heating networks are provided in Sections 2 and 3. In Section 4 the piping installation design is optimized in order to reduce costs wherever possible, without jeopardizing overall system efficiency, reliability or service life, and employing a mixture of typical US and European district-heating practices. The status of prospective non-metallic piping materials is presented in Section 5. The following materials have been investigated: fiberglass reinforced plastic, cross-linked polyethylene, polybutylene, prestressed concrete, polymer concrete, and asbestos-cement piping. (MCW)

Heat transfer and pressure drop results are presented for pipe flow of aqueous solutions of polyacrylamide and polyethylene oxide in weight concentration of a few thousand parts per million. Experiments were conducted in two experimental set-ups. The first set-up consisted of two different diameter tubes. The turbulent flow hydrodynamic entry length was found to be 110 pipe diameters. Laminar friction factor data were in good agreement with correlations for purely viscous non-Newtonian fluids. The second set-up consisted of three different diameter tubes with heat transfer length-to-diameter ratio of 282, 489, and 648. The turbulent flow thermal entry length was found to be about 400 pipe diameters. The asymptotic dimensionless heat transfer coefficients were observed to be independent of pipe diameter, polymer molecular weight, and polymer concentration, suggesting the existence of a maximum heat transfer reduction asymptote.

The effect of noncondensable gases on high-performance arterial heatpipes was investigated both analytically and experimentally. Models have been generated which characterize the dissolution of gases in condensate, and the diffusional loss of dissolved gases from condensate in arterial flow. These processes, and others, were used to postulate stability criteria for arterial heatpipes under isothermal and non-isothermal condensate flow conditions. A rigorous second-order gas-loaded heatpipe model, incorporating axial conduction and one-dimensional vapor transport, was produced and used for thermal and gas studies. A Freon-22 (CHCIF2) heatpipe was used with helium and xenon to validate modeling. With helium, experimental data compared well with theory. Unusual gas-control effects with xenon were attributed to high solubility.

Liquid-metal heatpipes have exhibited difficulties starting up from a frozen-state. Inert gas loading is a possible solution to the frozen-state startup problem. The present study deals with the diffusion-controlled startup analysis and testing of an argon-loaded, 2-m-long, stainless steel-sodium heatpipe of the double-walled type with artery channel and long adiabatic section. A two-dimensional, quasi-steady state, binary vapor-gas diffusion model determined the energy transport rate of vapor at the diffusion front. The analytical solution to the diffusion problem provided the vapor flux, which in turn was used in the one-dimensional transient thermal model of the heatpipe to predict the time rate-of-change of temperature and position of the hot front. The experimental test results successfully demonstrated the startup of a gas-loaded sodium heatpipe and validated the diffusion model of the startup.

Refractory metal heatpipes developed during this project shall be subjected to various operating conditions to evaluate life-limiting corrosion factors. To accomplish this objective, various parameters shall be investigated, including the effect of temperature and mass fluence on long-term corrosion rate. The test series will begin with a performance test of one module to evaluate its performance and to establish the temperature and power settings for the remaining modules. The performance test will be followed by round-the-clock testing of 16 heatpipes. All heatpipes shall be nondestructively inspected at 6-month intervals. At longer intervals, specific modules will be destructively evaluated. Both the nondestructive and destructive evaluations shall be coordinated with Los Alamos National Laboratory. During the processing, setup, and testing of the heatpipes, standard operating procedures shall be developed. Initial procedures are listed here and, as hardware is developed, will be updated, incorporating findings and lessons learned.

Optimization of double pipe helical coil heat exchanger with various optimizing parameters and its comparison with double pipe straight tube are the prime objectives of this paper. Numerical studies were performed with the aid of a commercial computational fluid dynamics package ANSYS FLUENT 14. In this paper the double pipe helical coil is analysed under turbulent flow conditions for optimum heat exchanger properties. The parameters used for optimization are cross-sectional shape and taper angles. Optimization analysis is being carried out for finding best cross sectional shape of heat exchanger coils by using rectangular, square, triangular and circular cross-sections. The tapered double pipe helical coil is then analysed for best heat transfer and pressure drop characteristics by varying the angle of taper. Finally, an optimum coil on the basis of all the analysis is selected. This optimized double pipe helical coil is compared with double pipe straight tube of equivalent cross-sectional area and length as that of unwounded length of double pipe helical coil.

Pipe-soil interaction has to be taken into account in the design of district heating (DH) pipes. The investigation presented here focuses on the effect of the reduction of axial friction forces due to cyclic axial displacements and the corresponding stress redistribution. Calculations with a three-dimensional finite element model were carried out in which a standard situation of a buried DH pipe was studied. A significant reduction of friction with cyclic axial displacements was obtained, although no temperature loading and thus no radial expansion of the pipe was considered. The reason for the friction force decrease is a densification of the soil beneath the pipe, which leads to a decrease of the normal stress acting between pipe and soil.

A novel design of a high-temperature axially grooved heatpipe (HP), which utilizes thermal energy storage (TES) to mitigate pulse heat loads, was presented. Phase-change material (PCM) encapsulated in cylindrical containers was used for thermal energy storage. The transient responses of the HP/TES system under two types of pulse heat loads were studied numerically. The first type is pulse heat loads applied at the heatpipe evaporator; the second type is reversed-pulse heat loads applied at the condenser. The transient response of three different HP/TES configurations were compared: (1) a heatpipe with a large empty cylinder installed in the vapor core, (2) a heatpipe with a large PCM cylinder, and (3) a heatpipe with six small PCM cylinders. It was found that the PCM is very effective in mitigating the adverse effect of pulse heat loads. The six small PCM cylinders are more efficient than the large PCM cylinder in relaxing the heatpipe temperature increase under pulse heat loads.

The work focuses on the mathematical modeling of three critical mechanisms of heat-pipe operation: (1) the effect that excess liquid has on heat-pipe performance; (2) the calculation of the dryout limit of circumferential grooves; (3) an efficient mathematical model for the calculation of the viscous-inertial interaction in the vapor flow. These mathematical models are incorporated in the computer program GRADE II, which is described.

The application of variable conductance heatpipe technology for achieving precise temperature control to + or - 0.1 C for a space-based laser diode transmitter is described. Heatpipe theory of operation and test data are presented along with a discussion of its applicability for NASA's Direct Detection Laser Transceiver (DDLT) program. This design for the DDLT transmitter features a reduction in space radiator size and up to 42 percent reduction in prime power requirements.

Experimental investigation is carried out to study the thermal performance of a heat sink with finned U-shape heatpipes which is a contemporary central processing unit (CPU) cooler compatible for a wide range of high-frequency microprocessors. The optimum range of operating heat load based on thermal resistance analysis of the heat sink is characterized. The convection heat transfer coefficient between the fins and the ambient air is estimated by using Bessel's modified equation in conjunction with the results obtained through the experimental investigation. The thermal optimization of the heat sink involves the determination of the optimized L-ratio (ratio of the evaporator section length to the condenser section length) of the U-shape heatpipe, by evaluating the minima of the thermal resistance function, in which case the empirical convection heat transfer coefficient is applied in the calculation. In conjunction with this, the optimal L-ratio of a U-shape heatpipe is found to be dependent on other geometrical parameters such as the heatpipe diameter and the fin spacing, which are of practical engineering importance in the optimum design of the heat sink. (author)

In order to investigate root cause of the pipe rupture, which took place at the Hamaoka Nuclear Power Station Unit-1 of Chubu Electric Power Company on November 7, 2001, a task force was established within the Nuclear and Industrial Safety Agency (NISA) and initiated a detailed investigation of the ruptured pipe. The Japan Atomic Energy Research Institute (JAERI) was asked from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) in response to the request from NISA to cooperate as an independent neutral organization with NISA and perform an examination of the ruptured pipe independently from Chubu Electric Power Company. JAERI accepted the request by considering the fact that JAERI is an integrated research institution for nuclear research and development, a prime research institution for nuclear safety research, a research institution with experience of root-cause investigation of various nuclear incidents and accidents of domestic as well as overseas, and a research institution provided with advanced examination facilities necessary for examination of the ruptured pipe. The JAERI examination group was formed at the Tokai Research Establishment and conducted detailed and thorough examination of the pieces taken from the ruptured pipe primarily in the Reactor Fuel Examination Facility (RFEF) with the use of tools such as scanning electron microscopes and other equipments. Purpose of examination was to provide technical information in order to identify causes of the pipe rupture through examination of the pieces taken from the ruptured region of the pipe. The following findings and conclusion were made as the result of the present examination. (1) Wall thickness of the pipe was significantly reduced in the ruptured region. (2) Dimple pattern resulting from ductile fracture by shearing was observed in the fracture surfaces of nearly all of the pieces and no indication of fatigue crack growth was found. (3) Microstructure showed a typical carbon

Heatpipe cooling for battery thermal management systems (BTMSs) in electric vehicles (EVs) is growing due to its advantages of high cooling efficiency, compact structure and flexible geometry. Considering the transient conduction, phase change and uncertain thermal conditions in a heatpipe, it is challenging to obtain the dynamic thermal characteristics accurately in such complex heat and mass transfer process. In this paper, a "segmented" thermal resistance model of a heatpipe is proposed based on thermal circuit method. The equivalent conductivities of different segments, viz. the evaporator and condenser of pipe, are used to determine their own thermal parameters and conditions integrated into the thermal model of battery for a complete three-dimensional (3D) computational fluid dynamics (CFD) simulation. The proposed "segmented" model shows more precise than the "non-segmented" model by the comparison of simulated and experimental temperature distribution and variation of an ultra-thin micro heatpipe (UMHP) battery pack, and has less calculation error to obtain dynamic thermal behavior for exact thermal design, management and control of heatpipe BTMSs. Using the "segmented" model, the cooling effect of the UMHP pack with different natural/forced convection and arrangements is predicted, and the results correspond well to the tests.

In this study, we theoretically investigate the thermal performances of heatpipes that have different nano-fluid properties. Two different types of nano-particles have been used: Al{sub 2}O{sub 3} and CuO. The thermal performances of the heatpipes are observed for varying nano-particle aggregations and volume fractions. Both the viscosity and the conductivity increase as the volume fraction and the aggregation increase, respectively. Increasing the volume fraction helps increase the capillary limit in the well-dispersed condition. Whereas, the capillary limit is decreased under the aggregate condition, when the volume fraction increases. The dependence of the heatpipe thermal resistance on the volume fraction, aggregation, and conductivity of the nano-particles is analyzed. The maximum thermal transfer of the heatpipe is highly dependent on the volume fraction because of the high permeability of the heatpipe. For the proposed heatpipe, the optimum volume fraction of the nano-particle can be seen through 3D graphics.

Full Text Available The paper presents the development and research results for a coaxial heatpipe designed for cooling of a reflector of a solid-state laser. A coaxial cylindrical heatpipe, designed to cool the laser reflector, provides that the temperature of the heat-removing surface does not exceed 120°C at any orientation in the gravitational field, if the heat is removed by forced convection of air with the temperature of 60°C in a pulsed mode of heat flow supply of 300 W. Thermal resistance of the developed heatpipe is 0,03 K/W, the specific thermal resistance — 1,1•10–3 m2•K/W. The developed cooling system based on the evaporation-condensation principle, allows ensuring temperature uniformity of the cooling surface at low thermal resistance.

Hydrogen explosions may occur simultaneously with water hammer accidents in nuclear facilities, and a theoretical mechanism to relate water hammer to hydrogen deflagrations and explosions is presented herein. Hydrogen and oxygen generation due to the radiolysis of water is a recognized hazard in pipe systems used in the nuclear industry, where the accumulation of hydrogen and oxygen at high points in the pipe system is expected, and explosive conditions may occur. Pipe ruptures in nuclear reactor cooling systems were attributed to hydrogen explosions inside pipelines, i.e., Hamaoka, Nuclear Power Station in Japan, and Brunsbuettel in Germany. Prior to these accidents, an ignition source for hydrogen was not clearly demonstrated, but these accidents demonstrated that a mechanism was, in fact, available to initiate combustion and explosion. A new theory to identify an ignition source and explosion cause is presented here, and further research is recommended to fully understand this explosion mechanism.

Full Text Available New energy-saving technologies for lighting is a promising trend in lighting technology. To this end, during the recent decade, have been actively developed and implemented lighting units based on LED modules. Reliability of such devices is largely dependent on the ensuring of cooling of the LEDs. Heatpipes are being used with ever increasing frequency for increasing an efficiency of cooling of powerful LEDs within a lightening device. Results of experimental modeling of thermal characteristics of two aluminum heatpipes with grooved capillary structure and ammonia used as a heat transfer agent, designed for application as a heat transfer elements in designs of powerful LED lightening device with forced air cooling are presented in this paper. It is shown that for the heat flux range of 50 to 100 W and for incident flow speed in the range of 0.8 to 2.1 m/s the temperature in the heating zone of the heatpipe falls into the range of 31.0 to 52.5 °C. In this case the temperature difference along the heatpipe is between 0.9…1.7 °C, when a minimal value of the fed heat flux is 50 W, and 1.7…3.1°C, when a maximum value of the heat flux is 100 W. The value of heat transfer resistance of the heatpipes was in the range of 0.012 to 0.044 °C/W. The key factors influencing the thermal characteristics of the heatpipes are: the value of the fed heat flux, the speed of cooling air flux, heatpipe inclination angle with respect to the horizon. By using five such heatpipes within the powerful LED lightning device it is possible to achieve an elimination of the total heat flux from LED modules up to 500 W. At an efficiency factor of LEDs of about 75% this is equivalent to intake power 665 W. Taking into account that luminous efficiency of modern LEDs is about 10 times as high as those of incandescent lamps, proposed lightning device will produce a luminous flux which is equivalent to the luminous flux of a lightening device with incandescent lamps

Currently the problem with the increasing number of electronic devices is a problem with the outlet Joule heating. Joule heating, also known as ohmic heating and resistive heating, is the process by which the passage of an electric current through a conductor releases heat. Perfect dustproof cooling of electronic components ensures longer life of the equipment. One of more alternatives of heat transfer without the using of mechanical equipment is the use of the heatpipe. Heatpipes are easy to manufacture and maintenance of low input investment cost. The advantage of using the heatpipe is its use in hermetic closed electronic device which is separated exchange of air between the device and the environment. This experiment deals with the influence of changes in the working tube diameter and changing the working fluid on performance parameters. Changing the working fluid and the tube diameter changes the thermal performance of the heatpipe. The result of this paper is finding the optimal diameter with ideal working substance for the greatest heat transfer for 1cm2 sectional area tube.

A Cesium HeatPipe has been constructed to produce a cesium metal vapor for use in laser spectroscopy. The heatpipe consists of a 24 inch stainless steel pipe with 2 inch diameter calcium fluoride windows on each end. Electric heaters are used to control the cesium vapor pressure. An argon buffer gas is used to maintain high transmittance through the end windows. Sensors are used to monitor both temperature and pressure. A Nd:YAG-pumped dye laser system is used to probe the cesium atoms via resonance ionization spectroscopy. Details of the construction of the heatpipe and the experimental setup will be presented. The results of the resonance ionization spectroscopy will be discussed. This experimental setup can be utilized with undergraduates in courses such as Optics, Laser Physics, and Senior Laboratory/Research.

energy between zones with one hydronic circuit, operating with a water temperature between 20°C and 23°C. To calculate the energy performance of the system, simulation-based research was developed. The two-pipe system was modelled by using EnergyPlus, a whole building energy simulation program. Hourly......The aim of this paper was to investigate the energy savings potential of an innovative two-pipe system in an active chilled beam application for heating and cooling of office buildings. The characteristic of the system is its ability to provide simultaneous heating and cooling by transferring...... heating, cooling and ventilation loads were calculated by the program and an annual energy consumption evaluation of the system was made. Simulation results showed that the innovative two-pipe active chilled beam system used approximately 5% less energy than a conventional four-pipe system....

Highlights: • Thermal aging embrittlement was considered in the PFM analysis of nuclearpipe. • Predicting program for pipe failure probability was developed based on thermal aging. • Cumulative failure probability is significantly affected by fracture toughness. • Cumulative failure probability is slightly affected by fatigue crack growth rate. • Tensile strength increase due to thermal aging slightly reduces pipe failure risk. - Abstract: A predicting program for pipe break probability based on thermal aging embrittlement was developed. In order for life prediction, evolutions of fracture toughness and tensile strength were estimated for a Z3CN20-09M piping steel using the Argonne National Laboratory (ANL) procedure. To understand the influence of thermal aging on failure probability, different evolutions of fracture toughness, tensile strength and fatigue crack growth rate were employed in the prediction of cumulative failure probability. The results show that the cumulative failure probability for 40-year thermal aging increases by almost four times compared to without consideration of fracture toughness degradation. The cumulative failure probability is slightly affected by fatigue crack growth rate. The increase of tensile strength due to thermal aging reduces the risk of pipe failure. This work demonstrates that the degradation of fracture toughness due to thermal aging should be fully considered in the probabilistic fracture mechanics analysis of nuclear pressure pipes.

In a seismic isolation nuclear facility, crossover piping system is subjected to large relative displacement and inertia forces during earthquakes. Hinged bellows expansion joints are utilized for accommodation to such the large displacement. This report describes tests for validation of developed simulation code with analytical models. Seismic experiments by a vibration test machine were conducted using actual size piping system models. A comparison between test results and analytical results showed a favorable agreement. The vibration test demonstrated that the structural integrity of this piping system would be maintained during earthquakes. (H. Itami)

A study on the application of cooling defect detection was performed on the basis of a preceding study on the heated defect detection in nuclearpiping loop system, using lock-in infrared thermography. A loop system with piping defects was made by varying the wall-thinning length, the circumference orientation angle, and the wall-thinning depth. The test was performed using an IR camera and a cooling device. Distance between the cooling device and the target loop system was fixed at 2 m. For analyzing experimental results, the temperature distribution data for cooling, and phase data were obtained. Through the analysis of this data, the defect length was measured. The reliability of the measurements for cooling defect conditions was shown to be higher in the lock-in infrared thermography data than the infrared thermography data.

The aim of this study was to investigate the possibility of analysing the temperature profile at the ground surface above buried district heatingpipes in such a way that would enable the quantitative determination of heat loss from the pair of pipes. In practical applications, it is supposed that this temperature profile is generated by means of advanced IR-thermography. For this purpose, the principle of the TX - model has been developed, based on the fact that the heat losses from pipes buried in the ground have a temperature signature on the ground surface. Qualitative analysis of this temperature signature is very well known and in practical use for detecting leaks from pipes. These techniques primarily make use of relative changes of the temperature pattern along the pipe. In the quantitative heat loss analysis, however, it is presumed that the temperature profile across the pipes is related to the pipeheat loss per unit length. The basic idea is that the integral of the temperature profile perpendicular to the pipe, called TX, is a function of the heat loss, but is also affected by other parameters such as burial depth, heat diffusivity, wind, precipitation and so on. In order to analyse the parameters influencing the TX- factor, a simulation model for the energy balance at the ground surface has been developed. This model includes the heat flow from the pipe to the surface and the heat exchange at the surface with the environment due to convection, latent heat change, solar and long wave radiation. The simulation gives the surprising result that the TX factor is by and large unaffected during the course of a day even when the sun is shining, as long as other climate conditions are relatively stable (low wind, no rain, no shadows). The results from the simulations were verified at different sites in Denmark, Finland, Sweden and USA through a co-operative research program organised and partially financed by the IEA District Heating Programme, Task III, and

MEMS微型热管作为一种新型的热管技术,在微电子、光电池、红外探测头和激光二极管等的热控制方面具有很大的应用前景.首先,介绍了MEMS微型热管的特点和基本工作原理,简单回顾了其发展历程.然后,从MEMS微型热管的加工制作方法、通道尺寸和总体结构特点出发,指出了其优势所在.在此基础上,综述了近年来微型槽道热管、微型毛细泵回路、微型回路热管和微型振荡热管等不同类型MEMS微型热管的研究进展.最后,总结了MEMS微型热管的发展趋势和实际应用所面临的挑战,指出降低制作成本、优化工质充注封装工艺、改进测试手段和加强运行机理研究是今后工作的重点.%The MEMS micro heatpipe, as a novel heatpipe technology, is considered as one of the most promising choices for thermal control applications in microelectronics, photovoltaic cells, infrared detectors, laser diodes, etc. The basic principle and characteristics of MEMS micro heatpipes are firstly introduced, and the development history of which is reviewed briefly. Then, the fabrication method, channel size, and overall structure feature are compared with those of a traditional heatpipe, which account for the advantages of a MEMS micro heatpipe. Based on the discussion above, the progress of the micro grooved heatpipe, micro capillary pumped loop, micro loop heatpipe, micro pulsating heatpipe and other different types of the MEMS micro heatpipes are thoroughly reviewed. Finally, the development tendency and challenges impacting on real applications of MEMS micro heatpipes are prospected, and it is pointed out that the fabrication cost reduction, working fluid filling and packaging optimization, testing method improvement, as well as operational mechanism investigation are identified as major issues for the future research.

Full Text Available An experimental study on pulsating heatpipe (PHP is presented in this work. A closed loop PHP with a single U
turn is fabricated and tested. The transient and steady state experiments are conducted and operating temperatures are
measured. The experiments are carried out for different working fluids, heat input and for different evacuation levels.
The derived parameters include thermal resistance and heat transfer coefficient of PHP. The results of these
experiments show an intermittent motion of the working fluid at lower heat input. The temperature difference
between evaporator and condenser at steady state is found lower for acetone compared to water, ethanol and
methanol. Lower value of thermal resistance and higher value of heat transfer coefficient are observed in case of
acetone compared to water, ethanol and methanol. Lower values of temperature difference between evaporator and
condenser and thermal resistance and higher value of heat transfer coefficient are observed at atmospheric conditions
of operation of PHP compared to evacuation conditions. The Power Spectral Density Analysis is also carried out on
the results of these experiments using FFT technique to analyse the pulsating motion of the fluid in a PHP. In the
Power Spectral Density analysis, the frequency distribution of temperature variation in PHP was observed over a
wider range, signifying the periodic motion in the fluid flow of the liquid slug and vapour plug. This characteristic
frequency corresponded to the characteristic time for a couple of adjacent vapour plug and liquid slug passing
through a specific local wall surface in a PHP.

The SAFE-I00a test article at the NASA Marshall Space Flight Center was used to simulate a variety of potential reactor transients; the SAFEl00a is a resistively heated, stainless-steel heat-pipe (HP)-reactor core segment, coupled to a gas-flow heat exchanger (HX). For these transients the core power was controlled by a point kinetics model with reactivity feedback based on core average temperature; the neutron generation time and the temperature feedback coefficient are provided as model inputs. This type of non-nuclear test is expected to provide reasonable approximation of reactor transient behavior because reactivity feedback is very simple in a compact fast reactor (simple, negative, and relatively monotonic temperature feedback, caused mostly by thermal expansion) and calculations show there are no significant reactivity effects associated with fluid in the HP (the worth of the entire inventory of Na in the core is .

This study conducted infrared (IR) thermography tests using pipe and plate specimens with artificial wall-thinning defects to find an optimal condition for IR thermography test on the wall-thinned nuclearpiping components. In the experiment halogen lamp was used to heat the specimens. The distance between the specimen and the lamp and the intensity of halogen lamp were regarded as experimental parameter. When the distance was set to 1{approx}2 m and the lamp intensity was above 60 % of full power, a single scanning of IR thermography detected all artificial wall-thinning defects, whose minimum dimension was 2{theta} = 90 .deg., d/t=0.5, and L/D{sub o}, within the pipe of 500 mm in length. Regardless of the distance between the specimen and the lamp, the image of wall-thinning defect in IR thermography became distinctive as the intensity of halogen lamp increased. The detectability of IR thermography was similar for both plate and pipe specimens, but the optimal test condition for IR thermography depended on the type of specimen.

This paper elaborates on the testing of solar heatpipes using different working fluids, fill ratios and tilt angles. Methanol, Acetone and water are used as working fluids, with fill ratios 25%, 50%, 75% and 100%. Experiments were carried out at 600 and 350 inclinations. Heatpipe condenser section is placed inside a water basin containing 200ml of water. The evaporator section is exposed to sunlight where the working fluid gets heated and it becomes vapour and moves towards the condenser section. In the condenser section the heat is given to the water in the basin and the vapour becomes liquid and comes back to the evaporator section due to gravitational force. Two modes of experiments are carried out: 1) using a parabolic collector and 2) using heatpipe with evacuated tubes. On comparative study, optimum fill ratio is been found to be 25% in every case and acetone exhibited slightly more efficiency than methanol and water. As far as the heatpipe orientation is concerned, 600 inclination of the heatpipe showed better performance than 350

Sodium heatpipes have been identified as a potentially effective heat transport approach for CSP systems that require near-isothermal input to power cycles or storage, such as dish Stirling and highly recuperated reheat-cycle supercritical CO2 turbines. Heatpipes offer high heat flux capabilities, leading to small receivers, as well as low exergetic losses through isothermal coupling with the engine. Sandia developed a felt metal wick approach in the 1990's, and demonstrated very high performance1. However, multiple durability issues arose, primarily the structural collapse of the wick at temperature over short time periods. NTUU developed several methods of improving robustness of the wick2, but the resulting wick had limited performance capabilities. For application to CSP systems, the wick structures must retain high heatpipe performance with robustness for long term operation. In this paper we present our findings in developing an optimal balance between performance and ruggedness, including operation of a laboratory-scale heatpipe for over 5500 hours so far. Application of heatpipes to dish-Stirling systems has been shown to increase performance as much as 20%3, and application to supercritical CO2 systems has been proposed.

An approximate theoretical model is derived for laminar film condensation on the inside of a rotating, truncated cone, and is used to predict the heat transfer performance of rotating, non-capillary heatpipes for a wide variety of parametric conditions. Experimental results are presented for water, ethyl alcohol, and freon-113 in a stainless steel heatpipe rotating to speeds of 2800 rpm. Results show that these devices can be used effectively to transfer large quantities of heat in rotating systems. Predicted results agree to within + or - 20 percent of the experimental data. Dropwise condensation, instead of film condensation, improves heatpipe performance while the presence of non-condensible gases impairs performance.

Work initiated on a common-module thermal test simulation was continued, and a second project on heatpipe simulation was begun. The test bed, constructed from surplus Skylab equipment, was modeled and solved for various thermal load and flow conditions. Low thermal load caused the radiator fluid, Coolanol 25, to thicken due to its temperature avoided by using a regenerator-heat-exchanger. Other possible solutions modeled include a radiator heater and shunting heat from the central thermal bus to the radiator. Also, module air temperature can become excessive with high avionics load. A second preoject concerning advanced heatpipe concepts was initiated. A program was written which calculates fluid physical properties, liquid and vapor pressure in the evaporator and condenser, fluid flow rates, and thermal flux. The program is directed to evaluating newer heatpipe wicks and geometries, especially water in an artery surrounded by six vapor channels. Effects of temperature, groove and slot dimensions, and wick properties are reported.

Four kinds of micro heatpipe of trapezoidal groove wick structure with different numbers of grooves or aspect ratios were studied and compared about thermal transfer performances in order to optimize the manufacture of micro heatpipe with groove wick structure. The results show that these micro heatpipes have excellent performance in heat transfer; the equivalent thermal conductivity coefficient is two orders of magnitude compared with that of copper; the number and aspect ratio of grooves have a prominent effect on the performance of such thermal transfer. The optimum number of grooves is lower than 60 and the best aspect ratio is near to 1.5. The temperature and thermal transport rate are almost directly proportional relationship, but this relationship will be broken up suddenly when the critical heat flux is reached.

Full Text Available In this paper, a heatpipe evacuated tube solar collector has been investigated both theoretically and experimentally. A detailed theoretical method for energy and exergy analysis of the collector is provided. The method is also evaluated by experiments. The results showed a good agreement between the experiment and theory. Using the theoretical model, the effect of different parameters on the collector’s energy and exergy efficiency has been investigated. It is concluded that inlet water temperature, inlet water mass flow rate, the transmittance of tubes and absorptance of the absorber surface have a direct effect on the energy and exergy efficiency of the heatpipe evacuated tube solar collector. Increasing water inlet temperature in heatpipe evacuated solar collectors leads to a decrease in heat transfer rate between the heat pipe’s condenser and water.

Heat-transfer pipe rupture detection of steam generator is an important content of the reactor process monitoring. The producing mechanism of tritium in nuclear power plant loop water and the transition process of tritium in loop water under accident were discussed firstly. And then, the radioactive concentration of tritium in primary and secondary loop water from four nuclear power plants were measured respectively by using liquid scintillation counter. Experimental results show that the activity concentration of tritium in the purified primary loop water is at least two orders of magnitude, namely 633, 893, 188 and 394 times higher than that of the secondary loop water respectively. This indicates that it would be feasible to diagnose the heat-transfer pipe rupture detection of steam generator by monitoring the radioactive concentration of tritium in secondary loop water, however, further research of on-line monitoring techniques of tritium is needed.%蒸汽发生器传热管易发生破损,对其破损进行监测是反应堆工艺监测的重要内容之一.分析了核动力装置回路水中氚的产生机理及事故情况下氚在回路水中的迁移过程,利用液体闪烁计数器测量了4个核动力装置一、二回路水中氚的放射性活度浓度.结果表明,一回路水净化后的氚放射性活度浓度与相应的二回路水相比高出2个数量级,分别为633,893,188和394倍,可见利用二回路水中氚的放射性活度浓度来监测蒸汽发生器传热管是否发生破损是可行的.后期,还需对氚的在线实时监测开展深入研究.

The consistency between the experimental value of a soil temperature and the calculation value of a soil temperature given by a non-steady heat conduction equation was confirmed. The experimental value is obtained by laying a spiral heat exchange pipe in the heat-insulated soil box and circulating hot water forcibly in the pipe. The temperature conductivity in soil significantly influences the heat transfer in soil. The storage performance is improved when the temperature conductivity increases because of the contained moisture. As the difference between the initial soil temperature and circulating water temperature becomes greater, the heat storage and recovery values increase. A thermal core heat transfer is done in the spiral pipe. Therefore, the diameter of the pipe little influences the heat storage performance, and the pitch influences largely. About 50 hours after heat is stored, the storage performance is almost the same as for a straight pipe that uses the spiral diameter as a pipe diameter. To obtain the same heat storage value, the spiral pipe is made of fewer materials than the straight pipe and low in price. The spiral pipe is more advantageous than the straight pipe in the necessary motive power and supply heat of a pump. 1 ref., 11 figs., 1 tab.

Pulsating heatpipes (PHPs) are used as high efficiency heat exchangers, and the selection of working fluids in PHPs has a great impact on the heat transfer performance. This study investigates the thermal resistance characteristics of the PHP charged with acetone-based binary mixtures, where deionized water, methanol and ethanol were added to and mixed with acetone, respectively. The volume mixing ratios were 2:1, 4:1 and 7:1, and the heating power ranged from 10 to 100 W with filling ratios of 45, 55, 62 and 70%. At a low filling ratio (45%), the zeotropic characteristics of the binary mixtures have an influence on the heat transfer performance of the PHP. Adding water, which has a substantially different boiling point compared with that of acetone, can significantly improve the anti-dry-out ability inside the PHP. At a medium filling ratio (55%), the heat transfer performance of the PHP is affected by both phase transition characteristics and physical properties of working fluids. At high heating power, the thermal resistance of the PHP with acetone-water mixture is between that with pure acetone and pure water, whereas the thermal resistance of the PHP with acetone-methanol and acetone-ethanol mixtures at mixing ratios of 2:1 and 4:1 is less than that with the corresponding pure fluids. At high filling ratios (62 and 70%), the heat transfer performance of the PHP is mainly determined by the properties of working fluids that affects the flow resistance. Thus, the PHP with acetone-methanol and acetone-ethanol mixtures that have a lower flow resistance shows better heat transfer performance than that with acetone-water mixture.

Pulsating heatpipes (PHPs) are used as high efficiency heat exchangers, and the selection of working fluids in PHPs has a great impact on the heat transfer performance. This study investigates the thermal resistance characteristics of the PHP charged with acetone-based binary mixtures, where deionized water, methanol and ethanol were added to and mixed with acetone, respectively. The volume mixing ratios were 2:1, 4:1 and 7:1, and the heating power ranged from 10 to 100 W with filling ratios of 45, 55, 62 and 70%. At a low filling ratio (45%), the zeotropic characteristics of the binary mixtures have an influence on the heat transfer performance of the PHP. Adding water, which has a substantially different boiling point compared with that of acetone, can significantly improve the anti-dry-out ability inside the PHP. At a medium filling ratio (55%), the heat transfer performance of the PHP is affected by both phase transition characteristics and physical properties of working fluids. At high heating power, the thermal resistance of the PHP with acetone-water mixture is between that with pure acetone and pure water, whereas the thermal resistance of the PHP with acetone-methanol and acetone-ethanol mixtures at mixing ratios of 2:1 and 4:1 is less than that with the corresponding pure fluids. At high filling ratios (62 and 70%), the heat transfer performance of the PHP is mainly determined by the properties of working fluids that affects the flow resistance. Thus, the PHP with acetone-methanol and acetone-ethanol mixtures that have a lower flow resistance shows better heat transfer performance than that with acetone-water mixture.

The capacities of four, low-pressure fluid systems to withstand pressures and temperatures above the design levels were established for the Davis-Besse Nuclear Power Station. The results will be used in evaluating the probability of plant damage from Interfacing System Loss of Coolant Accidents (ISLOCA) as part of the probabilistic risk assessment of the Davis-Besse nuclear power station undertaken by EG G Idaho, Inc. Included in this evaluation are the tanks, heat exchangers, filters, pumps, valves, and flanged connections for each system. The probabilities of failure, as a function of internal pressure, are evaluated as well as the variabilities associated with them. Leak rates or leak areas are estimated for the controlling modes of failure. The pressure capacities for the pipes and vessels are evaluated using limit-state analyses for the various failure modes considered. The capacities are dependent on several factors, including the material properties, modeling assumptions, and the postulated failure criteria. The failure modes for gasketed-flange connections, valves, and pumps do not lend themselves to evaluation by conventional structural mechanics techniques and evaluation must rely primarily on the results from ongoing gasket research test programs and available vendor information and test data. 21 refs., 7 figs., 52 tabs.

Slush fluids such as slush hydrogen and slush nitrogen are characterized by superior properties as functional thermal fluids due to their density and heat of fusion. In addition to allowing efficient hydrogen transport and storage, slush hydrogen can serve as a refrigerant for high-temperature superconducting (HTS) equipment using MgB2, with the potential for synergistic effects. In this study, pressure drop reduction and heat transfer deterioration experiments were performed on slush nitrogen flowing in a horizontal triangular pipe with sides of 20 mm under the conditions of three different cross-sectional orientations. Experimental conditions consisted of flow velocity (0.3-4.2 m/s), solid fraction (0-25 wt.%), and heat flux (0, 10, and 20 kW/m2). Pressure drop reduction became apparent at flow velocities exceeding about 1.3-1.8 m/s, representing a maximum amount of reduction of 16-19% in comparison with liquid nitrogen, regardless of heating. Heat transfer deterioration was seen at flow velocities of over 1.2-1.8 m/s, for a maximum amount of deterioration of 13-16%. The authors of the current study compared the results for pressure drop reduction and heat transfer deterioration in triangular pipe with those obtained previously for circular and square pipes, clarifying differences in flow and heat transfer properties. Also, a correlation equation was obtained between the slush Reynolds number and the pipe friction factor, which is important in the estimation of pressure drop in unheated triangular pipe. Furthermore, a second correlation equation was derived between the modified slush Reynolds number and the pipe friction factor, enabling the integrated prediction of pressure drop in both unheated triangular and circular pipes.

Full Text Available Experimental investigation of heat transfer and friction factor characteristics in a double pipeheat exchanger with triangular fins was studied. The working fluids were air, flowing in the annular pipe, and water through the inner circular tube. The test section is consisting of two parts. The first part is an insulated tube which has been manufactured from Perspex material of (54mm inner diameter, (2000mm length and (3mm thickness. The second part is an internal copper tube without or with triangular copper fins. The smooth copper tube has (2250mm long and (20mm, 22mm inner and outer diameter respectively. The triangular fins were made of the copper with thickness of 0.3mm and 10mm height. They were installed on the straight copper tube section in three different cases (32, 27, and 22 mm distance between each two successive fins and (15mm pitch between each two of fins. Air at various mass flow rates (0.001875 to 0.003133 kg/sec flows through annuli and water at Reynold's numbers ranging from (10376.9 to 23348.03 flows through the inner tube. The inlet cold air and hot water temperatures are 30oC and 70oC, respectively. The experimental results showed an increase in convective heat transfer coefficient by decreasing in distance between two fins and by increasing Reynold's number. This is due to increase in surface area. It was found that (Space=22mm gives good heat transfer enhancement.

Heatpipe (HP)-based heat exchangers can be used for very low resistance heat transfer between a hot and a cold source. Their operating temperature depends solely on the boiling point of their working fluid, so it is possible to control the heat transfer temperature if the pressure of the HP can be adjusted. This is the case of the variable conductance HPs (VCHP). This solution makes VCHPs ideal for the passive control of thermoelectric generator (TEG) temperature levels. The present work assesses, both theoretically and experimentally, the merit of the aforementioned approach. A thermal and electrical model of a TEG with VCHP assist is proposed. Experimental results obtained with a proof of concept prototype attached to a small single-cylinder engine are presented and used to validate the model. It was found that the HP heat exchanger indeed enables the TEG to operate at a constant, optimal temperature in a passive and safe way, and with a minimal overall thermal resistance, under part load, it effectively reduces the active module area without deprecating the temperature level of the active modules.

Full Text Available This investigation was performed to experimentally investigate the enhancement of heat transfer and the friction of an annulus in a double pipeheat exchanger system with rectangular grooves in the turbulent flow regime. The shell is made of acrylic and its diameter is 28 mm. The tube is made of aluminium and its diameter is 20 mm. Grooves were incised in the annulus room with a circumferential pattern, with a groove space of 2 mm, a distance between the grooves of 8mm and a groove height of 0.3 mm. The experiments consist of temperature and pressure measurement and a flow visualization. Throughout the investigation, the cold fluid flowed in the annulus room. The Reynold number of cold fluid varied from about 31981 to 43601 in a counter flow condition. The volume flow rate of hot fluid remains constant with Reynold number about 30904. Result showed the effect of grooves, which are applied in the annulus room. The grooves induce the pressure drop, the pressure drop in the grooved annulus was greater by about 15.88% to 16.72% than the one in the smooth annulus. The total heat transfer enhancement is of 1.09–1.11. Moreover, the use of grooves in the annulus of the heat exchanger not only increase the heat transfer process, but also increase the pressure drop, which is related to the friction factor.

This paper deals with the performance characterization of heatpipes using an aqueous solution of long chain alcohols like n-Butanol, n-Pentanol, n-Hexanol and n-Heptanol as working mediums. These solutions are called as self-rewetting fluids, since these fluid mixtures possess a non-linear dependence of the surface tension with temperature. A cylindrical heatpipe made up of copper with two layers of wrapped screen is used as a wick material and partially filled with the self-rewetting fluid water mixture and tested for its heat transport capability like thermal efficiency and thermal resistance at different inclinations and input power levels. A number of tests have been performed with heatpipes, filled with various aqueous solutions of alcohols with a concentration of 2 ml/l in de-ionized water (DI water) on volume basis. The results obtained for heatpipes using self rewetting fluids show improved performances, when compared to DI water heatpipes. (orig.)

This paper deals with the performance characterization of heatpipes using an aqueous solution of long chain alcohols like n-Butanol, n-Pentanol, n-Hexanol and n-Heptanol as working mediums. These solutions are called as self-rewetting fluids, since these fluid mixtures possess a non-linear dependence of the surface tension with temperature. A cylindrical heatpipe made up of copper with two layers of wrapped screen is used as a wick material and partially filled with the self-rewetting fluid water mixture and tested for its heat transport capability like thermal efficiency and thermal resistance at different inclinations and input power levels. A number of tests have been performed with heatpipes, filled with various aqueous solutions of alcohols with a concentration of 2 ml/l in de-ionized water (DI water) on volume basis. The results obtained for heatpipes using self rewetting fluids show improved performances, when compared to DI water heatpipes.

One of the main challenges for the hypersonic vehicle is its thermal protection, more specifically, the cooling of its leading edge. To investigate the feasibility of a platelet heat-pipe-cooled leading edge structure, thermal/stress distributions for steady-state flight conditions are calculated numerically. Studies are carried on for IN718/Na, C-103/Na and T-111/Li compatible material combinations of heatpipe under nominal operations and a central heatpipe failure cases, and the influence of wall thickness on the design robustness is also investigated. And the heat transfer limits (the sonic limit, the capillary limit and the boiling limit) are also computed to check the operation of platelet heatpipes. The results indicate that, with a 15 mm leading edge radius and a wall thickness of 0.5 mm, C-103/Na and T-111/Li combinations of heatpipe is capable of withstanding both nominal and failure conditions for Mach 8 and Mach 10 flight respectively.

Thermal performance of a grooved heatpipe using aqueous nitrogen-doped graphene (NDG) nanofluids was analysed. This study in particular focused on the effect of varying NDG nanosheets concentrations, heatpipe inclination angles and input heating powers. The results indicated that the inclination...

1.2 Problem and Scope .. ............................. 3 1.3 Particle Bed Reactor .. .......................... 3 1.4 Nuclear Thermal Rocket .. ........................ 4...development of both the nuclear thermal rocket and space nuclear power technologies. The nuclear thermal rocket can be used to reduce the travel time to...1991). The manned mission to Mars is not the only use for the nuclear thermal rocket . Ramsthaler and Sulmeisters (1988:21) have determined that among

The philosophy of seismic design for nuclear power plant facilities in Japan is based on `Examination Guide for Seismic Design of Nuclear Power Reactor Facilities: Nuclear Power Safety Committee, July 20, 1981` (referred to as `Examination Guide` hereinafter) and the present design criteria have been established based on the survey of governmental improvement and standardization program. The detailed design implementation procedure is further described in `Technical Guidelines for Aseismic Design of Nuclear Power Plants, JEAG4601-1987: Japan Electric Association`. This report describes the principles and design procedure of the seismic design of equipment/piping systems for nuclear power plant in Japan. (J.P.N.)

A gas-loaded variable conductance heatpipe of stainless steel with methanol working fluid identical to one now on the CTS satellite was life tested in the laboratory at accelerated conditions for 14 200 hours, equivalent to about 70 000 hours at flight conditions. The noncondensible gas inventory increased about 20 percent over the original charge. The observed gas increase is estimated to increase operating temperature by about 2.2 C, insufficient to harm the electronic gear cooled by the heatpipes in the satellite. Tests of maximum heat input against evaporator elevation agree well with the manufacturer's predictions.

Full Text Available This paper presents an experimental investigation aimed at estimating the thermal efficiency of a heatpipe compared to the most common elements for removing heat from a circuit (i.e., an electric fan and a fin - extended surface. The input voltage frequency for a standard power circuit was changed for the experiments, whilst all the other parameters were kept constant. An experimental statistical design was used as an analytical tool. Unexpectedly, the heatpipe showed the lowest thermal efficiency for all the experiments, although it had the advantage of being a passive element having low volume and no mobile parts.

The vapor flow patterns in heatpipes are examined during the start-up transient phase. The vapor core is modelled as a channel flow using a two dimensional compressible flow model. A nonlinear filtering technique is used as a post process to eliminate the non-physical oscillations of the flow variables. For high-input heat flux, multiple shock reflections are observed in the evaporation region. The reflections cause a reverse flow in the evaporation and circulations in the adiabatic region. Furthermore, each shock reflection causes a significant increase in the local pressure and a large pressure drop along the heatpipe.

Full Text Available Heatpipes have been recently in use for cooling purposes in various fields, including electronic circuit boards and vehicle parts that generate large amounts of heat. In order to minimize the loss of heat transferred, there is a need to maximize the contact area of the working fluid. This study produced a square tube multi-channel heatpipe to replace the existing circular pipe type to maximize the internal surface area thereof. This expands the surface, allowing the working fluid to come into contact with a wider area and enhancing thermal radiation performance. A mold for the production for such a product was designed, and finite element simulation was performed to determine whether production is possible.

ANL/HTP is a computer code for the simulation of heatpipe operation, to predict heatpipe performance and temperature distributions during steady state operation. Source and sink temperatures and heat transfer coefficients can be set as input boundary conditions, and varied for parametric studies. Five code options are included to calculate performance for fixed operating conditions, or to vary any one of the four boundary conditions to determine the heatpipe limited performance. The performance limits included are viscous, sonic, entrainment capillary, and boiling, using the best available theories to model these effects. The code has built-in models for a number of wick configurations - open grooves, screen-covered grooves, screen-wrap, and arteries, with provision for expansion. The current version of the code includes the thermophysical properties of sodium as the working fluid in an expandable subroutine. The code-calculated performance agrees quite well with measured experiment data.

The problem of determining the feasibility of cooling hypersonic vehicle leading-edge structures exposed to severe aerodynamic surface heating using heatpipe and mass transfer cooling techniques is addressed. A description is presented of a numerical finite-difference-based hypersonic leading-edge cooling model incorporating poststartup liquid metal heatpipe cooling with surface transpiration and film cooling to predict the transient structural temperature distributions and maximum surface temperatures of hypersonic vehicle leading edge. An application of this model to the transient cooling of a typical aerospace plane wing leading-edge section. The results of this application indicated that liquid metal heatpipe cooling alone is insufficient to maintain surface temperatures below an assumed maximum level of 1800 K for about one-third of a typical aerospace plane ascent trajectory through the earth's atmosphere.

A collector/heatpipe cooled, externally configured (heated) thermionic diode module was designed for use in a laboratory test to demonstrate the applicability of this concept as the fuel element/converter module of an in-core thermionic electric power source. During the course of the program, this module evolved from a simple experimental mock-up into an advanced unit which was more reactor prototypical. Detailed analysis of all diode components led to their engineering design, fabrication, and assembly, with the exception of the collector/heatpipe. While several designs of high power annular wicked heatpipes were fabricated and tested, each exhibited unexpected performance difficulties. It was concluded that the basic cause of these problems was the formation of crud which interfered with the liquid flow in the annular passage of the evaporator region.

Integral heat-pipe sandwich panels, which synergistically combine the thermal efficiency of heatpipes and the structural efficiency of honeycomb sandwich panel construction, were fabricated and tested. The designs utilize two different wickable honeycomb cores, facesheets with screen mesh sintered to the internal surfaces, and potassium or sodium as the working fluid. Panels were tested by radiant heating, and the results indicate successful heatpipe operation at temperatures of approximately 922K (1200F). These panels, in addition to solving potential thermal stress problems in an Airframe-Integrated Scramjet Engine, have potential applications as cold plates for electronic component cooling, as radiators for space platforms, and as low distortion, large area structures.

Simulation work on an intermittent-duty, heatpipe-assisted, solar-operated aqua-ammonia absorption refrigerator is reported. The low-thermal mass collector is the integral evaporator of an acetone-copper heatpipe which delivers the collected energy isothermally to a distant generator. The shell-and-tube type generator receives the energy by vapour condensation. The condenser is air cooled. A separate R-22/steel heat-pipe system serves to cool the absorber tanks via a radiation/convection panel. Heat and mass balances are outlined on several units. The resulting equations are solved for day and night operation. It is concluded that both the initial solution (absorbent) concentration and the absorber temperature must be kept low for adequate ice production.

textabstractEndovenous laser ablation (EVLA) produces boiling bubbles emerging from pores within the hot fiber tip and traveling over a distal length of about 20 mm before condensing. This evaporation-condensation mechanism makes the vein act like a heatpipe, where very efficient heat transport mai

Endovenous laser ablation (EVLA) produces boiling bubbles emerging from pores within the hot fiber tip and traveling over a distal length of about 20 mm before condensing. This evaporation-condensation mechanism makes the vein act like a heatpipe, where very efficient heat transport maintains a con

Endovenous laser ablation (EVLA) produces boiling bubbles emerging from pores within the hot fiber tip and traveling over a distal length of about 20 mm before condensing. This evaporation-condensation mechanism makes the vein act like a heatpipe, where very efficient heat transport maintains a con

We investigate a novel evaporator design for a small-scale refrigeration system whose function is to assist the existing heatpipe technology currently used in chip cooling of portable computers. A heat transfer model for the evaporator/heatpipe assembly was devised specifically for sizing the evaporator in order to keep the chip surface temperature below a certain value. A prototype was tested with R-600a at saturation temperatures of 45 and 55 C, mass flow rates between 0.5 and 1.5 kg h{sup -1} and heat transfer rates between 30 and 60 W. The experimental results demonstrated that the average refrigerant-side heat transfer coefficient is more sensitive to a change in the refrigerant mass flux than to changes in the saturation temperature and heat transfer rate. The agreement between the calculated heat transfer coefficient and the data was within {+-}10% for the conditions evaluated. (author)

Sealing quality strongly affects heatpipe performance, but few studies focus on the process of heatpipe sealing. Cold welding sealing technology based on a stamping process is applied for heatpipe sealing. The bonding mechanism of the cold welding sealing process (CWSP) is investigated and compared with the experimental results obtained from the bonding interface analysis. An orthogonal experiment is conducted to observe the effects of various parameters, including the sealing gap, sealing length, sealing diameter, and sealing velocity on bonding strength. A method with the utilization of saturated vapor pressure inside a copper tube is proposed to evaluate bonding strength. A corresponding finite element model is developed to investigate the effects of sealing gap and sealing velocity on plastic deformation during the cold welding process. Effects of various parameters on the bonding strength are determined and it is found that the sealing gap is the most critical factor and that the sealing velocity contributes the least effect. The best parameter combination (A 1 B 3 C 1 D 3, with a 0.5 mm sealing gap, 6 mm sealing length, 3.8 mm sealing diameter, and 50 mm/s sealing velocity) is derived within the experimental parameters. Plastic deformation results derived from the finite element model are consistent with those from the experiment. The instruction for the CWSP of heatpipes and the design of sealing dies of heatpipes are provided.

Construction of India's Prototype Fast Breeder Reactor (PFBR) involves extensive welding of austenitic stainless steels pipes of different dimensions. Due to high thermal expansion coefficient and poor thermal conductivity of this class of steels, welding can result in significant distortion of these pipes. Attempts to arrest this distortion can lead to high levels of residual stresses in the welded parts. Heat sink welding is one of the techniques often employed to minimize distortion and residual stress in austenitic stainless steel pipe welding. This technique has also been employed to repair welding of the piping of the Boiling Water Reactors (BWRs) subjected to radiation induced intergranular stress corrosion cracking (IGSCC). In the present study, a comparison of the distortion in two pipe welds, one made with heat sink welding and another a normal welds. Pipes of dimensions 350{phi} x 250(L) x 8(t) mm was fabricated from 316LN plates of dimensions 1100 x 250 x 8 mm by bending and long seam (L-seam) welding by SMAW process. Two fit ups with a root gap of 2 mm, land height of 1mm and a groove angle of 70 were prepared using these pipes for circumferential seam (C-seam) welding. Dimensions at predetermined points in the fit up were made before and after welding to check the variation in radius, circumference and and ovality of the pipes. Root pass for both the pipe fit up were carried out using conventional GTAW process with 1.6 mm AWS ER 16-8-2 as consumables. Welding of one of the pipe fit ups were completed using conventions GTAW process while the other was completed using heat sink welding. For second and subsequent layers of welding using this process, water was sprayed at the root side of the joint while welding was in progress. Flow rate of the water was {proportional_to}6 1/minute. Welding parameters employed were same as those used for the other pipe weld. Results of the dimensional measurements showed that there is no circumferential shrinkage in

The study investigates the temporal performance of heatpipe using surfactant free Al2O3/De-ionised water nanofluids. The nanofluids prone to agglomeration and sedimentation with time are expected to influence the performance of heatpipe. Specially fabricated heatpipe is made to accommodate vapor velocity fluctuation through the vapor core and the end cap brazing effects. The heatpipe filled up to 40 % of the evaporator volume is tested at increasing volume concentration (0.005, 0.05, 0.5, 1 vol%) of Al2O3/De-ionised water nanofluid. The thermal performance of heatpipe is tested at three watt loads of heat input (12, 32, 72 W) and after successive durations (0, 3, 6, 9 months) from the date of manufacturing with non operational time span. The results are compared after successive time intervals and with deionised water as working fluid. Despite higher thermal performance of heatpipe observed using nanofluids as working fluids, consistency and reliability in heatpipe operating characteristics has been observed at high watt load heat input of 72 W as compared to low watt heat of 12 W. The thermal performance improvement of heatpipe using the nanofluid resulted due to nano-coating of Al2O3 nanoparticles on the mesh, resulting in localized high vapor pressure caused by the subsequent intermittent accelerated flow, reduction of contact angle and enhancement in boiling limit.

Full Text Available Thermal characteristics of turbulent nanofluid flow in a rectangular pipe have been investigated numerically. The continuity, momentum, and energy equations were solved by means of a finite volume method (FVM. The symmetrical rectangular channel is heated at the top and bottom at a constant heat flux while the sides walls are insulated. Four different types of nanoparticles Al2O3, ZnO, CuO, and SiO2 at different volume fractions of nanofluids in the range of 1% to 5% are considered in the present investigation. In this paper, effect of different Reynolds numbers in the range of 5000 < Re < 25000 on heat transfer characteristics of nanofluids flowing through the channel is investigated. The numerical results indicate that SiO2-water has the highest Nusselt number compared to other nanofluids while it has the lowest heat transfer coefficient due to low thermal conductivity. The Nusselt number increases with the increase of the Reynolds number and the volume fraction of nanoparticles. The results of simulation show a good agreement with the existing experimental correlations.

Thermal characteristics of turbulent nanofluid flow in a rectangular pipe have been investigated numerically. The continuity, momentum, and energy equations were solved by means of a finite volume method (FVM). The symmetrical rectangular channel is heated at the top and bottom at a constant heat flux while the sides walls are insulated. Four different types of nanoparticles Al2O3, ZnO, CuO, and SiO2 at different volume fractions of nanofluids in the range of 1% to 5% are considered in the present investigation. In this paper, effect of different Reynolds numbers in the range of 5000 < Re < 25000 on heat transfer characteristics of nanofluids flowing through the channel is investigated. The numerical results indicate that SiO2-water has the highest Nusselt number compared to other nanofluids while it has the lowest heat transfer coefficient due to low thermal conductivity. The Nusselt number increases with the increase of the Reynolds number and the volume fraction of nanoparticles. The results of simulation show a good agreement with the existing experimental correlations.

The results of a modeling and simulation study are presented for a combined system consisting of a gas turbine engine, a heatpipe recovery system and an inlet-air cooling system. The presentation covers performance data related to the gas turbine engine with precooled air intake as coupled to the water-in-copper heatpipe recovery system. This is done by matching the two mathematical models. The net power output is improved by 11% when the gas turbine engine is supplied with cold air produced by the heat-pipe recovery and utilization system. It is further concluded from the results produced by the combined mathematical model that the thermal efficiency of the gas turbine engine rises to 6% at 75% part load. It is to be anticipated that this rising trend in increases of thermal efficiency of the gas turbine engine would continue for operations at other (lower) part load conditions. (author)

The pre-insulated pipe cartel was established 1990 in Denmark, was extended to Italy and Germany during 1991 and re-organised in 1994 to cover the entire common market. Cartel members engaged in market sharing, price setting, bid rigging, coordinated predation and delaying of innovation. The Euro...

Heatpipes are two-phase heat transfer devices, which operate based on evaporation and condensation of a working fluid inside a sealed container. In the current work, an experimental study was conducted to investigate the performance of a copper-water heatpipe. The performance was evaluated by calculating the corresponding thermal resistance as the ratio of temperature difference between evaporator and condenser to heat input. The effects of inclination angle and the amount of working fluid were studied on the equivalent thermal resistance. The results showed that if the heatpipe is under-filled with the working fluid, energy transferring capacity of the heatpipe decreases dramatically. However, overfilling heatpipe causes over flood and degrades heatpipe performance. The minimum thermal resistances were obtained for the case that 30% of the heatpipe volume was filled with working fluid. It was also found that in gravity-assisted orientations, the inclination angle does not have significant effect on the performance of the heatpipe. However, for gravity-opposed orientations, as the inclination angle increases, the temperature difference between the evaporator and condensation increases and higher thermal resistances are obtained. Authors appreciate the financial support by a research Grant from Temple University.

The development effort for, and the fabrication and testing of, six CTS-type variable conductance heatpipes is described. The heatpipes are constructed of stainless steel, use methanol as a working fluid, and a nitrogen/helium mixture as the control gas. The wicking structure consists of interior wall grooves, a metal-felt diametral slab wick, and two wire-mesh arteries. The heatpipes are used to cool two Functional Model/Power Processing Units in a Solar Electric Propulsion prototype BIMOD thruster subsystem assembly. The Power Processing Units convert the electric power from a spacecraft solar array system to the voltages required to operate the electric thrusters which are part of the BIMOD assembly.

A theoretical investigation of the fluid flow and heat transferin a pipe with porous body of high porosity twis ted by metal wire was carried out. A theoretical model of a circular pipe with porous matrix attached at the channel wall and extended inward the centerline was set up. Through ana lyzing the flow in the porous matrix by the Brinkman-extend ed-Darcy equation and through including the effect of disper sion by adding the dispersion coefficient into the energy equa tion, the theoretical solutions of velocity distribution and temperature fields were obtained. Finally the effect of the properties of the porous matrix on the flow and heat transfer in the porous body was studied, which indicates that dispersion can really enhance the heat transfer in pipe.

The flow and heat transfer performances of horizontal spiral-coil pipes of circular and elliptical cross-sections are studied. The numerical results are compared with the experimental data, to verify the numerical method. The effects of the inlet water mass flow rate, the structural parameters, the helical pitch and the radius ratio on the heat transfer performances are investigated. Perfor- mances of the secondary fluid flow with different radius ratios are also investigated. Numerical results demonstrate that the heat transfer coefficient and the Nusselt number increase with the increase of the water mass flow rate or the helical pitch. The maximum heat transfer coefficient and the maximum Nusselt number are obtained when the radius ratio isequal to 1.00. In addition, the fluid particle moves spirally along the pipe and the velocity changes periodically. The particle flow intensity and the spiral movement frequency decrease significantly with the increase of the radius ratio. Besides, the secondary flow profile in the horizontal spiral-coil pipe contains two oppositely rotating eddies, and the eddy intensity decreases significantly along the pipe owing to the change of curvature. The decreasing tendency of the eddy intensity along the pipe increases with the increase of the radius ratio.

Sharp local structure, like the leading edge of hypersonic aircraft, confronts a severe aerodynamic heating environment at a Mach number greater than 5. To eliminate the danger of a material failure, a semi-active thermal protection system is proposed by integrating a metallic heatpipe into the structure of the leading edge. An analytical heat-balance model is established from traditional aerodynamic theories, and then thermal and mechanical characteristics of the structure are studied at Ma...

The district heating and cooling (DHC) system of a seawater-source heat pump is large system engineering. The investments and the operational cost of DHC pipe network are higher than a tradition system. Traditional design methods only satisfy the needs of the technology but dissatisfy the needs of the economy, which not only waste a mass of money but also bring problems to the operation, the maintenance and the management. So we build a least-annualized-cost global optimal mathematic model that comprises all constrict conditions. Furthermore, this model considers the variety of heating load and cooling load, the operational adjustment in different periods of the year. Genetic algorithm (GA) is used to obtain the optimal combinations of discrete diameters. Some operators of GA are selected to reduce the calculation time and obtain good calculation accuracy. This optimal method is used to the design of the DHC network of Xinghai Bay commercial district which is a real engineering. The design optimization can avoid the matter of the hydraulic unbalance of the system, enhance the running efficiency and greatly reduce the annualized-cost comparing with the traditional design method. (author)

An experimental facility is described for the recovery, by means of heat-pipes, of waste-heat from exhaust gases, and the utilization of the recovered energy to cool ambient air. To this end, heat of combustion gases, generated in a stainless-steel combustion chamber, is recovered from the stack by means of a heat-pipe system. The recovered heat is utilized to run a modified commercial aqua-ammonia absorption chiller. Chilled water from the chiller is supplied to a fan-coil type cooling tunnel to cool the intake air of a (conceptual) gas turbine engine to boost its performance. It is concluded from test results that the experimental facility performs well, and that it behaves as predicted by modeling and simulation studies. The system is able to extract between 70 and 93% of the technically recoverable energy from exhaust gases, and utilizes the extracted energy to cool air. (Author)

In this study, for the first time, it is tried to construct a pilot reactor, for surveying the possibility of creating isothermal condition in the catalytic convertors where SO2 is converted to SO3 in the sulfuric acid plants by heatpipe. The thermodynamic and thermo-kinetic conditions were considered the same as the sulfuric acid plants converters. Also, influence of SO2 gas flow rate on isothermal condition, has been studied. A thermo-siphon type heatpipe contains the sulfur + 5% iodine as working fluid, was used for disposing the heat of reaction from catalytic bed. Our results show that due to very high energy-efficiency, isothermal and passive heat transfer mechanism of heatpipe, it is possible to reach more than 95% conversion in one isothermal catalytic bed. As the results, heatpipe can be used as a certain piece of equipment to create isothermal condition in catalytic convertors of sulphuric acid plants. With this work a major evaluation in design of sulphuric acid plants can be taken place.

Heat-generating nuclear waste disposal in bedded salt during the first two years after waste emplacement is explored using numerical simulations tied to experiments of hydrous mineral dehydration. Heating impure salt samples to temperatures of 265 °C can release over 20% by mass of hydrous minerals as water. Three steps in a series of dehydration reactions are measured (65, 110, and 265 °C), and water loss associated with each step is averaged from experimental data into a water source model. Simulations using this dehydration model are used to predict temperature, moisture, and porosity after heating by 750-W waste canisters, assuming hydrous mineral mass fractions from 0 to 10%. The formation of a three-phase heatpipe (with counter-circulation of vapor and brine) occurs as water vapor is driven away from the heat source, condenses, and flows back toward the heat source, leading to changes in porosity, permeability, temperature, saturation, and thermal conductivity of the backfill salt surrounding the waste canisters. Heatpipe formation depends on temperature, moisture availability, and mobility. In certain cases, dehydration of hydrous minerals provides sufficient extra moisture to push the system into a sustained heatpipe, where simulations neglecting this process do not.

Full Text Available The data presented in this article were the basis for the study reported in the research articles entitled ‘Climate responsive behaviour heatpipe technology for enhanced passive airside cooling’ by Chaudhry and Hughes [10] which presents the passive airside cooling capability of heatpipes in response to gradually varying external temperatures and related to the research article “CFD and wind tunnel study of the performance of a uni-directional wind catcher with heat transfer devices” by Calautit and Hughes [1] which compares the ventilation performance of a standard roof mounted wind catcher and wind catcher incorporating the heatpipe technology. Here, we detail the wind tunnel test set-up and inflow conditions and the methodologies for the transient heatpipe experiment and analysis of the integration of heatpipes within the control domain of a wind catcher design.

The data presented in this article were the basis for the study reported in the research articles entitled 'Climate responsive behaviour heatpipe technology for enhanced passive airside cooling' by Chaudhry and Hughes [10] which presents the passive airside cooling capability of heatpipes in response to gradually varying external temperatures and related to the research article "CFD and wind tunnel study of the performance of a uni-directional wind catcher with heat transfer devices" by Calautit and Hughes [1] which compares the ventilation performance of a standard roof mounted wind catcher and wind catcher incorporating the heatpipe technology. Here, we detail the wind tunnel test set-up and inflow conditions and the methodologies for the transient heatpipe experiment and analysis of the integration of heatpipes within the control domain of a wind catcher design.

A compact and time effective insulation design procedure for solar heating system piping and water-filled thermal storage tanks was developed. Recognizing the particular sensitivity of solar systems to cost, the economic aspect of the problem is treated by a comprehensive present-value life-cycle cost analysis. In the development of the method, a numerical sensitivity analysis was performed to determine the relative effects of all relevant independent variables (within their pertinent ranges) on piping and tank heat transfer coefficient values.

This paper presents a method for the dimensioning of the low-energy District Heating (DH) piping networks operating with a control philosophy of supplying heat in low-temperature such as 55 °C in supply and 25°C in return regularly while the supply temperature levels are being boosted in cold...... winter periods. The performance of the existing radiators that were formerly sized with over-dimensions was analyzed, its results being used as input data for the performance evaluation of the piping network of the low-energy DH system operating with the control philosophy in question. The optimization...

Full Text Available The leak before break (LBB concept is widely used in designing pipe lines in nuclear power plants. According to the concept, the amount of leaking liquid from a pipe should be more than the minimum detectable leak rate of a leak detection system before catastrophic failure occurs. Therefore, accurate estimation of the leak rate is important to evaluate the validity of the LBB concept in pipe line design. In this paper, a program was developed to estimate the leak rate through circumferential cracks in pipes in nuclear power plants using the Henry–Fauske flow model and modified Henry–Fauske flow model. By using the developed program, the leak rate was calculated for a circumferential crack in a sample pipe, and the effect of the flow model on the leak rate was examined. Treating the crack morphology parameters as random variables, the statistical behavior of the leak rate was also examined. As a result, it was found that the crack morphology parameters have a strong effect on the leak rate and the statistical behavior of the leak rate can be simulated using normally distributed crack morphology parameters.

The heatpipes are devices that allow the transportation of large heat quantities with high thermal efficiency, by using the effect of a work fluid vaporization and condensation inside a sealed tube, resulting in a heat average conduction with 100 to 1000 times higher than a massive copper tube with the same diameter. This paper discusses the increasing of the thermal efficiency and the incentives to the using of natural gas with heatpipe.

This research aims to develop snow melting system around steel top of underground fire cistern by using heatpipe, for realizing quick finding of the steel top under heavy snow fall. Water in a fire cistern installed underground is heated by underground heat source, 10 ~15 °C. The iron top is put on snow melting panel made of reinforced concrete. Heat is transported from water to the snow melting panel by heatpipes, which melts snow on it. The experimental results obtained for two years show that this system can melt the snow around the steel top in winter season preferably. The numerical simulation using only weather data was found to predict temperature variations of the whole system with good agreements to the experimental data. Therefore, this simulation software can be used for designing this snow-melting system.

The development of a capillary pump loop (CPL) heatpipe, including computer modeling and breadboard testing, is presented. The computer model is a SINDA-type thermal analyzer, combined with a pressure analyzer, which predicts the transients of the CPL heatpipe during operation. The breadboard is an aluminum/ammonia transport system which contains multiple parallel evaporator and condenser zones within a single loop. Test results have demonstrated the practicality and reliability of such a design, including heat load sharing among evaporators, liquid inventory/temperature control feature, and priming under load. Transport capability for this system is 65 KW-M with individual evaporator pumps managing up to 1.7 KW at a heat flux of 15 W/sq cm. The prediction of the computer model for heat transport capabilities is in good agreement with experimental results.

This workshop on heatpipes and two-phase capillary pumping loops was organized by the French society of thermal engineers. The 11 papers presented during this workshop deal with the study of thermal performances of heatpipes and on their applications in power electronics (cooling of components), and their use in satellites, aircrafts and trains. (J.S.)

A new thermal control system based on heatpipe to support the development of a primary lithium/thionyl chloride (Li/SOCl2) battery designed for future space applications is shown. Performances of the used heatpipe are considered and range performances of a traditional cell cooling concept based on the use of an aluminum pipe put around the cell and fixed to a coldplate is shown. A mock up was carried out and compared to thermal model of the whole system using ESACAP software. This model includes about 120 nodes to present the cell and the aluminum pipe. These results are compared to those of the proposed new cooling concept based on a grooved nickel/F11 heatpipe integrated in the cell. In this case, a mock up was performed and a corresponding nodal model was built. The experimental and modeling results show that the new concept decreases thermal gradient and weight and increases the available current discharge rate compared with the traditional cooling concept.

Full Text Available Heat transfer in double pipeheat exchanger with circumference-rectangular grooves has been investigated experimentally. The volume flowrate of cold and hot water were varied to determine its influence on the approach temperature of the outlet terminals. In this experimental design, the grooves were incised in annular room that is placed on the outside surface of the inner pipe. The shell diameter is 38.1 mm and tube diameter 19.4 mm with 1 m length, which is made of aluminum. The flow pattern of the two fluids in the heat exchanger is a parallel flow. The working fluid is water with volume flow rate of 27.1, 23.8 and 19.8 l/minute. The temperature of water on the inlet terminals are 50±1°C for hot stream and 30±1°C for cold stream. Temperature measurements conducted on each terminal of the inlet and outlet heat exchanger. The results showed that the grooves induced the approach temperature. The change of the approach temperature from the grooves compared to that of without grooves decreased by 37.9%. This phenomenon indicates an increase in heat transfer process and performance of the heat exchanger. Groove improves the heat surface area of the inner pipe, increasing the momentum transfer and in the other hand, reducing the weight of heat exchangers itself.

Highlights: • The critical points of a seismically isolated NPP piping system are identified. • The simulation results are validated through a monotonic and cyclic test of the critical points. • The conditional mean spectrum method is used to scale the selected records. • The fragility curves of the NPP piping system are estimated. • Computation of the fragility parameters is addressed. - Abstract: Nuclear power plants are high risk facilities due to the possibility of sudden seismic events, because any possible failure could initiate catastrophic radioactive contamination. The seismic fragility analysis of NPPs and related equipments (such as piping systems) is a proven method to determine their performance against any possible earthquake. In this study the Brookhaven National laboratory benchmark model of a piping system was considered for the fragility analysis. A tensile test was conducted to define the material properties. An initial seismic analysis of the piping system is performed to indicate the critical sections of the piping system. Numerical analysis was validated through a monotonic and cyclic loading experiment of two identified critical points of the piping system. The tests were conducted at the Korea Construction Engineering Development (KOCED) Seismic Simulation Test Center, Pusan National University, Korea. Fragility curves were expressed for critical points of the system as a function of the spectral acceleration of the records and the maximum relative displacement. The standard deviation of the response and capacity were calculated using mathematical formulas, assuming that those follow a log-normal distribution. We determined that the fragility curve of a pipe elbow must be derived for both the opening and closing mode, regarding the difference between the capacities of the elbow on those modes. The high confidence of low probability of failure for the considered fragility functions in a straight section in any direction is

The focus of this work was to establish an approach to generate carefully controlled data that can conclusively establish heatpipe operating life with material-fluid combinations capable of extended operation. To accomplish this goal acceleration is required to compress 10 years of operational life into 3 years of laboratory testing through a combination of increased temperature and mass fluence. Specific test series have been identi3ed, based on American Society for Testing and Materials (ASTM) specifications, to investigate long term corrosion rates. The refractory metal selected for demonstration purposes is a Molybdenum-44.5%Rhenium alloy formed by powder metallurgy. The heatpipe makes use of an annular crescent wick design formed by hot isostatic pressing of Molybdenum-Rhenium wire mesh. The heatpipes are filled using vacuum distillation and purity sampling is considered. Testing of these units is round-the-clock with 6-month destructive and non-destructive inspection intervals to identify the onset and level of corrosion. Non-contact techniques are employed for providing power to the evaporator (radio frequency induction heating at I to 5 kW per unit) and calorimetry at the condenser (static gas gap coupled water cooled calorimeter). The planned operating temperature range would extend from 1123 to 1323 K. Accomplishments prior to project cancellation included successful demonstration of the heatpipe wick fabrication technique, establishment of all engineering designs, baselined operational test requirements and procurement/assembly of supporting test hardware systems.

Swirl flow is of great stature in heat transfer enhancement and in numerous engineering applications. In the present numerical study, the swirl flow of water in a circular pipe is considered. Here the Reynolds Number is kept within 2000. The pipe contains stationary blades to produce the swirl flow. The blades are considered heat resistant. The three-dimensional Navier-Stokes equations for incompressible Newtonian fluid flow are used. The code is corroborated by comparing the simulation results with the established Hagen-Poiseuille law. The comparison is quite satisfactory and thus the code is used for present investigation. In this study, the heat transfer performance of the swirl flow is evaluated. Two cases are considered on the outer surface of the pipe: (i) Constant heat flux and (ii) Constant temperature. This investigation reveals that the swirl flow increases the mean outlet temperature in both cases. The effects of the vane angle, pipe length and diameter on heat transfer characteristics are also evaluated.

In the real functioning of flat micro heatpipe (FMHP), there can appear cases when the temperature from the vaporization zone can exceed a critical value caused by a sudden increase of the thermal flow. The heat transfer which is completed conductively through the copper wall of a FMHP vaporizer causes the vaporization of the work fluid. On the condenser, the condensation of the fluid vapors and the transfer of the condenser to the vaporizer can no longer be achieved. The solution proposed for enhancing heat transfer in the event of blockage phenomenon FMHP, it is the injection of a certain amount of working fluid in the vaporization zone. By this process the working fluid injected into the evaporator passes suddenly in the vapor, producing a cooling zone. The new product additional mass of vapor will leave the vaporization zone and will condense in condensation zone, thereby supplementing the amount of condensation. Thus resumes normal operating cycle of FMHP. For the experimental measurements made for the transfer of heat through the FMHP working fluid demineralized water, they were made two micro-capillary tubes of sintered copper layer. The first was filled with 1ml of demineralized water was dropped under vacuum until the internal pressure has reached a level of 1•104Pa. The second FMHP was filled with the same amount of working fluid was used and the same capillary inner layer over which was laid a polysynthetic material that will accrue an additional amount of fluid. In this case, the internal pressure was reduced to 1•104Pa.

Full Text Available Cost and effectiveness are two important factors of heatpipeheat exchanger (HPHE design. The total cost includes the investment cost for buying equipment (heat exchanger surface area and operating cost for energy expenditures (related to fan power. The HPHE was thermally modeled using e-NTU method to estimate the overall heat transfer coefficient for the bank of finned tubes as well as estimating pressure drop. Fast and elitist non-dominated sorting genetic algorithm (NSGA-II with continuous and discrete variables was applied to obtain the maximum effectiveness and the minimum total cost as two objective functions. Pipe diameter, pipe length, numbers of pipes per row, number of rows, fin pitch and fin length ratio were considered as six design parameters. The results of optimal designs were a set of multiple optimum solutions, called ‘Pareto optimal solutions’. The comparison of the optimum values of total cost and effectiveness, variation of optimum values of design parameters as well as estimating the payback period were also reported for various inlet fresh air volume flow rates.

In order to enhance the heat transfer coefficient of the fin used in the finned tube heat exchanger, newly designed fin surfaces, especially, with small diameter (≅4mm) pipes are developed. The experiments are made by the transient testing technique, and used the plastic fins scaling up 4 times of the actual metal fin size. The data of the heat transfer coefficient and the pressure drop are transformed to the actual metal fin data. The fin with the anomalous staggered pipe arrangement and the bridge-like cutting-out with inclined leg portion from stream line is found to have very high overall heat transfer coefficient which is about 1.8-fold increase in comparison with the conventional Louvered fin. In this paper the reason why such enhancement is caused is clarified by mean of the calculation based on the rectangular duct flow. The calculated values are coincident with the data of the experiment well.

This report summarizes work in the Heat-pipe Technology Development for the Advanced Energy Transport Concepts program for the period January 1999 through September 2001. A gas-loaded molybdenum-sodium heatpipe was built to demonstrate the active pressure-control principle applied to a refractory metal heatpipe. Other work during the period included the development of processing procedures for and fabrication and testing of three types of sodium heatpipes using Haynes 230, MA 754, and MA 956 wall materials to assess the compatibility of these materials with sodium. Also during this period, tests were executed to measure the response of a sodium heatpipe to the penetration of water.

The feasibility of competitive, modular bulk electric power from the sun may be greatly enhanced by the use of a reflux heatpipe receiver to combine a heat engine with a paraboloidal dish concentrator. This combination represents a potential improvement over previous successful demonstrations of dish-electric technology in terms of enhanced performance, lower cost, longer life, and greater flexibility in engine design. In the reflux (i.e., gravity assisted) heatpipe receiver, concentrated solar radiation causes liquid metal (sodium, potassium, or NaK) to evaporate. The vapor flows to the engine interface heat exchanger, where it condenses and releases the latent heat. The condensate is returned to the receiver absorber by gravity (refluxing), and distributed over the surface by gravity and/or capillary forces in a wick lining the receiver. It is essentially an adaptation of heatpipe technology to the peculiar requirements of concentrated solar flux, and provides many advantages over conventional heated tub receiver technology. This overview paper describes the current status and future plans for the U.S. Solar Thermal Program reflux receiver development program at Sandia National Laboratories. Current work includes conventional mesh wick receivers, sintered metal wicks, and pool boiler receivers. The relative design merits and concerns of the different approaches and technology development test plans are discussed.

An investigation was conducted to study the feasibility of cooling hypersonic vehicle leading edge structures exposed to severe aerodynamic surface heat fluxes using a combination of liquid metal heatpipes and surface mass transfer cooling techniques. A generalized, transient, finite difference based hypersonic leading edge cooling model was developed that incorporated these effects and was demonstrated on an assumed aerospace plane-type wing leading edge section and a SCRAMJET engine inlet leading edge section. The hypersonic leading edge cooling model was developed using an existing, experimentally verified heatpipe model. Two applications of the hypersonic leading edge cooling model were examined. An assumed aerospace plane-type wing leading edge section exposed to a severe laminar, hypersonic aerodynamic surface heat flux was studied. A second application of the hypersonic leading edge cooling model was conducted on an assumed one-quarter inch nose diameter SCRAMJET engine inlet leading edge section exposed to both a transient laminar, hypersonic aerodynamic surface heat flux and a type 4 shock interference surface heat flux. The investigation led to the conclusion that cooling leading edge structures exposed to severe hypersonic flight environments using a combination of liquid metal heatpipe, surface transpiration, and film cooling methods appeared feasible.

Next-generation heat-pipe radiator technologies are being developed at the NASA Glenn Research Center to provide advancements in heat-rejection systems for space power and propulsion systems. All spacecraft power and propulsion systems require their waste heat to be rejected to space in order to function at their desired design conditions. The thermal efficiency of these heat-rejection systems, balanced with structural requirements, directly affect the total mass of the system. Terrestrially, this technology could be used for thermal control of structural systems. One potential use is radiant heating systems for residential and commercial applications. The thin cross section and efficient heat transportability could easily be applied to flooring and wall structures that could evenly heat large surface areas. Using this heat-pipe technology, the evaporator of the radiators could be heated using any household heat source (electric, gas, etc.), which would vaporize the internal working fluid and carry the heat to the condenser sections (walls and/or floors). The temperature could be easily controlled, providing a comfortable and affordable living environment. Investigating the appropriate materials and working fluids is needed to determine this application's potential success and usage.

An experimental study and theoretical analysis of heat transfer performance of a sintered heatpipe radiator that implemented in a 50 L domestic semiconductor refrigerator have been conducted to examine the effect of inclination angle, combined with a minimum entropy generation analysis. The experiment results suggest that inclination angle has influences on both the evaporator and condenser section, and the performance of the heatpipe radiator is more sensitive to the inclination change in negative inclined than in positive inclined position. When the heatpipe radiator is in negative inclination angle position, large amplitude of variation on the thermal resistance of this heatpipe radiator is observed. As the thermal load is below 58.89 W, the influence of inclination angle on the overall thermal resistance is not that apparent as compared to the other three thermal loads. Thermal resistance of heatpipe radiator decreases by 82.86 % in inclination of 60° at the set of 138.46 W, compared to horizontal position. Based on the analysis results in this paper, in order to achieve a better heat transfer performance of the heatpipe radiator, it is recommended that the heatpipe radiator be mounted in positive inclination angle positions (30°-90°), where the condenser is above the evaporator.

An experimental study and theoretical analysis of heat transfer performance of a sintered heatpipe radiator that implemented in a 50 L domestic semiconductor refrigerator have been conducted to examine the effect of inclination angle, combined with a minimum entropy generation analysis. The experiment results suggest that inclination angle has influences on both the evaporator and condenser section, and the performance of the heatpipe radiator is more sensitive to the inclination change in negative inclined than in positive inclined position. When the heatpipe radiator is in negative inclination angle position, large amplitude of variation on the thermal resistance of this heatpipe radiator is observed. As the thermal load is below 58.89 W, the influence of inclination angle on the overall thermal resistance is not that apparent as compared to the other three thermal loads. Thermal resistance of heatpipe radiator decreases by 82.86 % in inclination of 60° at the set of 138.46 W, compared to horizontal position. Based on the analysis results in this paper, in order to achieve a better heat transfer performance of the heatpipe radiator, it is recommended that the heatpipe radiator be mounted in positive inclination angle positions (30°-90°), where the condenser is above the evaporator.

In order to compete with steel, a fibre-reinforced composite exhaust wall with a general-purpose resin system requires an effective but lightweight insulation layer. However a lack of experimental methods for heat transfer from turbulent gas flow to pipe walls lined with a porous insulation layer wa

In order to compete with steel, a fibre-reinforced composite exhaust wall with a general-purpose resin system requires an effective but lightweight insulation layer. However a lack of experimental methods for heat transfer from turbulent gas flow to pipe walls lined with a porous insulation layer

The integration of low-cost commercial heatpipes in the design of a NASA candidate standard modular power supply with a 350 watt output resulted in a 44% weight reduction. Part temperatures were also appreciably reduced, increasing the environmental capability of the unit. A complete 350- watt modular power converter was built and tested to evaluate thermal performance of the redesigned supply.

A novel, integrated approach in thermal management of electronic products, based on two-phase cooling, is presented. A flat miniature heatpipe, integrated inside the laminated structure of a printed circuit board (PCB) has been developed, based on mainstream PCB fabrication processes. Hot spots on

Endovenous laser ablation (EVLA) produces boiling bubbles emerging from pores within the hot fiber tip and traveling over a distal length of about 20 mm before condensing. This evaporation-condensation mechanism makes the vein act like a heatpipe, where very efficient heat transport maintains a constant temperature, the saturation temperature of 100 degrees C, over the volume where these non-condensing bubbles exist. During EVLA the above-mentioned observations indicate that a venous cylindrical volume with a length of about 20 mm is kept at 100 degrees C. Pullback velocities of a few mm/s then cause at least the upper part of the treated vein wall to remain close to 100 degrees C for a time sufficient to cause irreversible injury. In conclusion, we propose that the mechanism of action of boiling bubbles during EVLA is an efficient heat-pipe resembling way of heating of the vein wall.

Full Text Available The leak before break (LBB concept is well known to nuclear power reactor. The problem is common to water power reactor. This is based on the premise that a detectable leak will develop before catastrophic break occurs. The main purpose of the present study is to develop tape cast MgCr2O4+35mole% TiO2 and gel cast g-Al2O3 humidity sensor for use in LBB applications at 3000C. The material capacitance varies with transient injection of water vapour adsorption. In actual plant, the sensors are placed on a steam pipe surrounded by heat insulation. The pipe unites the nuclear reactor and power generator. The analysis of humidity distribution in the annulus is calculated assuring leak rate 0.1gpm in a 30 m long tube. In this paper, analysis is done on the basis of the two types of sensor using AC frequency. Performance characteristics are observed for the LLB application.

The report describes a program to develop and demonstrate in the 600 to 1600 C temperature range the heat transfer potential of heatpipes using a novel, high performance wick structure. The tunnel wick as conceived at Thermacore makes use of the high capillary pressure provided by the sinterng of finely divided metal powders. Low resistance liquid flow passages, or tunnels, are formed within the sintered powder. Theoretical analysis predicts higher performance for these structures than any demonstrated in the world to date.

The heat transport capacity of traditional heatpipes is limited by the capillary pressure generated in the internal wick that pumps condensate to the evaporator. Recently, the authors conceptualized a novel heatpipe architecture, wherein wick-based pumping is replaced by electrowetting (EW)-based pumping of microliter droplets in the adiabatic section. An electrowetting heatpipe (EHP) can overcome the capillary limit to heat transport capacity and enable compact, planar, gravity-insensitive, and ultralow power consumption heatpipes that transport kiloWatt heat loads over extended distances. This work develops a novel technique for rapid, scalable fabrication of EW-based devices and studies critical microfluidic operations underlying the EHP, with the objective of predicting the key performance parameters of the EHP. Devices are fabricated on a printed circuit board (PCB) substrate with mechanically-milled electrodes, and a removable polyimide dielectric film. The first set of experiments uncovers the maximum channel gap (1 mm) for reliable EW-based pumping; this parameter determines the heat transport capacity of the EHP, which scales linearly with the channel gap. The second set of experiments uncovers the maximum channel gap (375 microns) at which EW voltages can successfully split droplets. This is an important consideration which ensures EHP operability in the event of unintentional droplet merging. The third set of experiments demonstrate and study EW-induced droplet generation from an open-to-air reservoir, which mimics the interface between the condenser and adiabatic sections of the EHP. The experimental findings predict that planar, water-based EHPs with a (10 cm by 4 mm) cross section can transport 1.6 kW over extended distances (>1 m), with a thermal resistance of 0.01 K W-1.

Erosion/corrosion in single-phase piping systems was not clearly recognized as a potential safety issue before the pipe rupture incident at the Surry Power Station in December 1986. This incident reminded the nuclear industry and the regulators that neither the U.S. Nuclear Regulatory Commission (NRC) nor Section XI of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code require utilities to monitor erosion/corrosion in the secondary systems of nuclear power plants. This report provides a brief review of the erosion/corrosion phenomenon and its major occurrences in nuclear power plants. In addition, efforts by the NRC, the industry, and the ASME Section XI Committee to address this issue are described. Finally, results of the survey and plant audits conducted by the NRC to assess the extent of erosion/corrosion-induced piping degradation and the status of program implementation regarding erosion/corrosion monitoring are discussed. This report will support a staff recommendation for an additional regulatory requirement concerning erosion/corrosion monitoring.

This study explores a method of generating electricity while recovering waste heat through the integration of heatpipes and thermoelectric generators (i.e. HPTEG system). The simultaneous waste heat recovery and power generation processes are achieved without the use of any moving parts. The HPTEG system consists of bismuth telluride thermoelectric generators (TEG), which are sandwiched between two finned pipes to achieve a temperature gradient across the TEG for electricity generation. A counter-flow heat exchanger was built using two separate air ducts. The air ducts were thermally coupled using the HPTEG modules. The evaporator section of the heatpipe absorbed the waste heat in a hot air duct. The heat was then transferred across the TEG surfaces. The condenser section of the HPTEG collected the excess heat from the TEG cold side before releasing it to the cold air duct. A 2-kW electrical heater was installed in the hot air duct to simulate the exhaust gas. An air blower was installed at the inlet of each duct to direct the flow of air into the ducts. A theoretical model was developed for predicting the performance of the HPTEG system using the effectiveness-number of transfer units method. The developed model was able to predict the thermal and electrical output of the HPTEG, along with the rate of heat transfer. The results showed that by increasing the cold air velocity, the effectiveness of the heat exchanger was able to be increased from approximately 52% to 58%. As a consequence of the improved heat transfer, maximum power output of 4.3 W was obtained.

We report the design, experimental setup and successful test results using an innovative passive cooling system called a “Pulsating Heat Pipe” (PHP) operating at temperatures ranging from 77 K to 80 K and using nitrogen as the working fluid. PHPs, which transfer heat by two phase flow mechanisms through a closed loop tubing have the advantage that no electrical pumps are needed to drive the fluid flow. In addition, PHPs have an advantage over copper straps and thermal conductors since they are lighter in weight, exhibit lower temperature gradients and have higher heat transfer rates. PHPs consist of an evaporator section, thermally anchored to a solid, where heat is received at the saturation temperature where the liquid portion of the two-phase flow evaporates, and a condenser where heat is rejected at the saturation temperature where the vapor is condensed. The condenser section in our experiment has been thermally interfaced to a CT cryocooler from SunPower that has a cooling capacity of 10 W at 77 K. Alternating regions of liquid slugs and small vapor plugs fill the capillary tubing, with the vapor regions contracting in the condenser section and expanding in the evaporator section due to an electric heater that will generate heat loads up to 10 W. This volumetric expansion and contraction provides the oscillatory flow of the fluid throughout the capillary tubing thereby transferring heat from one end to the other. The thermal performance and temperature characteristics of the PHP will be correlated as a function of average condenser temperature, PHP fill liquid ratio, and evaporator heat load. The experimental data show that the heat transfer between the evaporator and condenser sections can produce an effective thermal conductivity up to 35000 W/m-K at a 3.5 W heat load.

Heatpipes are widely used for the thermal control of electronic devices due to their capability of heat transport at high rate over considerable distance with small temperature drop. This study investigates the experimental performance of the heatpipe using the combination of copper nanofluids and the different types of aqueous solution of long chain alcohols. An experimental system is set up to measure the temperature distribution of heatpipes along the surface to determine the thermal efficiency and the thermal resistance of different working fluids computed. The working fluids used in this analysis illustrate certain improvement in the metrics over the conventional working fluids, pertaining to the heat transport limitations. The experimental results display higher efficiency and lower thermal resistance of the heatpipe when compared with the conventional working fluids like water.

A preliminary analysis has been performed examining the temperature distribution in the Divertor Primary Heat Transfer System (PHTS) piping and the divertor itself during the gas baking process. During gas baking, it is required that the divertor reach a temperature of 350 C. Thermal losses in the piping and from the divertor itself require that the gas supply temperature be maintained above that temperature in order to ensure that all of the divertor components reach the required temperature. The analysis described in this report was conducted in order to estimate the required supply temperature from the gas heater.

National Aeronautics and Space Administration — While continuously increasing in complexity, the payloads of terrestrial high altitude balloons need a thermal management system to reject their waste heat and to...

Full Text Available In this paper, influence of void ratio on phase change of thermal storage unit for heatpipe receiver under microgravity is numerically simulated. Accordingly, mathematical model is set up. A solidification-melting model upon the enthalpy-porosity method is specially provided to deal with phase changes. The liquid fraction distribution of thermal storage unit of heatpipe receiver is shown. The fluctuation of melting ratio in PCM canister is indicated. Numerical results are compared with experimental ones in Japan. The results show that void cavity prevents the process of phase change greatly. PCM melts slowly during sunlight periods and freezes slowly during eclipse periods as void ratio increases. The utility ratio of PCM during both sunlight periods and eclipse periods decreases obviously with the improvement of void ratio. The thermal resistance of void cavity is much higher than that of PCM canister wall. Void cavity prevents the heat transfer between PCM zone and canister wall.

The transient operation of the liquid phase of a high temperature heatpipe is studied. The study was conducted in support of advanced heatpipe applications that require reliable transport of high temperature drops and significant distances under a broad spectrum of operating conditions. The heatpipe configuration studied consists of a sealed cylindrical enclosure containing a capillary wick structure and sodium working fluid. The wick is an annular flow channel configuration formed between the enclosure interior wall and a concentric cylindrical tube of fine pore screen. The study approach is analytical through the solution of the governing equations. The energy equation is solved over the pipe wall and liquid region using the finite difference Peaceman-Rachford alternating direction implicit numerical method. The continuity and momentum equations are solved over the liquid region by the integral method. The energy equation and liquid dynamics equation are tightly coupled due to the phase change process at the liquid-vapor interface. A kinetic theory model is used to define the phase change process in terms of the temperature jump between the liquid-vapor surface and the bulk vapor. Extensive auxiliary relations, including sodium properties as functions of temperature, are used to close the analytical system. The solution procedure is implemented in a FORTRAN algorithm with some optimization features to take advantage of the IBM System/370 Model 3090 vectorization facility. The code was intended for coupling to a vapor phase algorithm so that the entire heatpipe problem could be solved. As a test of code capabilities, the vapor phase was approximated in a simple manner.

Effective thermal control systems are essential for reliable operation of spacecraft.A dual-driven intelligent combination control strategy is proposed to improve the temperate control and heat flux tracking effects.Both temperature regulation and heat flux tracking errors are employed to generate the final control action; their contributions are adaptively adjusted by a fuzzy fusing policy of control actions.To evaluate the control effects,describe a four-nodal mathematical model for analyzing the dynamic characteristics of the controlled heatpipe space cooling system (HP-SCS) consisting of an aluminum-ammonia heatpipe and a variable-emittance micro-electromechanical-system (MEMS) radiator.This dynamical model calculates the mass flow-rate and condensing pressure of the heatpipe working fluid directly from the systemic nodal temperatures,therefore,it is more suitable for control engineering applications.The closed-loop transient performances of four different control schemes have been numerically investigated.The results conclude that the proposed intelligent combination control scheme not only improves the thermal control effects but also benefits the safe operation of HP-SCS.

In this paper, a novel approach has been presented to simulate and optimize the pulsating heatpipes (PHPs). The used pulsating heatpipe setup was designed and constructed for this study. Due to the lack of a general mathematical model for exact analysis of the PHPs, a method has been applied for simulation and optimization using the natural algorithms. In this way, the simulator consists of a kind of multilayer perceptron neural network, which is trained by experimental results obtained from our PHP setup. The results show that the complex behavior of PHPs can be successfully described by the non-linear structure of this simulator. The input variables of the neural network are input heat flux to evaporator (q″), filling ratio (FR) and inclined angle (IA) and its output is thermal resistance of PHP. Finally, based upon the simulation results and considering the heatpipe's operating constraints, the optimum operating point of the system is obtained by using genetic algorithm (GA). The experimental results show that the optimum FR (38.25 %), input heat flux to evaporator (39.93 W) and IA (55°) that obtained from GA are acceptable.

In this paper, a novel approach has been presented to simulate and optimize the pulsating heatpipes (PHPs). The used pulsating heatpipe setup was designed and constructed for this study. Due to the lack of a general mathematical model for exact analysis of the PHPs, a method has been applied for simulation and optimization using the natural algorithms. In this way, the simulator consists of a kind of multilayer perceptron neural network, which is trained by experimental results obtained from our PHP setup. The results show that the complex behavior of PHPs can be successfully described by the non-linear structure of this simulator. The input variables of the neural network are input heat flux to evaporator (q″), filling ratio (FR) and inclined angle (IA) and its output is thermal resistance of PHP. Finally, based upon the simulation results and considering the heatpipe's operating constraints, the optimum operating point of the system is obtained by using genetic algorithm (GA). The experimental results show that the optimum FR (38.25 %), input heat flux to evaporator (39.93 W) and IA (55°) that obtained from GA are acceptable.

In the first part of the report, we review various efforts that have been recently performed in the USA in the field of reactor health monitoring. They were carried out by different organizations and they addressed different issues related to the safety of nuclear reactors. Among other aspects, we present technical issues related to the design of a self-diagnostic monitoring system for the next generation of nuclear reactors. We also give a brief review of the international experience of such systems in today's reactors. In the second part of the report we focus on long range ultrasonic techniques that can be used for monitoring piping in nuclear reactors. Common strategy used in the Swedish nuclear plants is leak before break (LBB), which relies on monitoring leaks from the pipelines as indications of possible pipe break. Significant parts of piping systems are partly or entirely inaccessible for the NDE inspectors, which complicates the use of proactive strategies. One solution to the problem could be implementing monitoring systems capable of monitoring pipelines over a long range. The method, which has shown much promise in such applications is the UT based on guided waves (GW) referred to as long range ultrasound testing (LRUT). In the report we give a brief review of the GW theory followed by the presentation the commercial GW instruments and transducers designed for the LRUT of piping. We also present examples of the baseline based systems using permanently installed transducers. In the final part we report capacity tests of the LRUT instruments performed in collaboration with two different manufactures.

Full Text Available The paper contains results of the investigations pertaining to thermodynamic steam characteristics of the operating pipe-line, analysis of steam flow regimes, influence of heat losses on temperature fall along the length. The eh-diagram presents changes in e and e values which are caused by decrease of mean temperatures with the given pressure value at pipe-line inlet and outlet. The paper shows that steam enthalpy at the pipeline outlet depends on inlet enthalpy, ambient temperature and entropy difference.The constructed nomograph makes it possible to forecast steam temperature fall in the pipe-line with the purpose to ensure more efficient usage of its thermodynamic potential.

This paper summarizes work on angled through-wall-crack initiation and combined loading effects on ferritic nuclearpipe performed as part of the Nuclear Regulatory Commission`s research program entitled {open_quotes}Short Cracks In Piping an Piping Welds{close_quotes}. The reader is referred to Reference 1 for details of the experiments and analyses conducted as part of this program. The major impetus for this work stemmed from the observation that initially circumferentially oriented cracks in carbon steel pipes exhibited a high tendency to grow at a different angle when the cracked pipes were subjected to bending or bending plus pressure loads. This failure mode was little understood, and the effect of angled crack grown from an initially circumferential crack raised questions about how cracks in a piping system subjected to combined loading with torsional stresses would behave. There were three major efforts undertaken in this study. The first involved a literature review to assess the causes of toughness anisotropy in ferritic pipes and to develop strength and toughness data as a function of angle from the circumferential plane. The second effort was an attempt to develop a screening criterion based on toughness anisotropy and to compare this screening criterion with experimental pipe fracture data. The third and more significant effort involved finite element analyses to examine why cracks grow at an angle and what is the effect of combined loads with torsional stresses on a circumferentially cracked pipe. These three efforts are summarized.

Full Text Available The use of low-potential heat is now possible especially in systems using heat pumps. There is a presumption that the trend will continue. Therefore, there is a need to find ways to be systems with a heat pump efficiencies. The usage of heatpipes seems to be an appropriate alternative to the establishedtechnology of obtaining heat through in-debt probes. This article describes a series of experiments on simulator for obtaining low-potential geothermal energy, in order to find the optimal amount of carbon dioxide per meter length of the heatpipe. For orientation and understanding of the conclusions of theexperiment, the article has also a detailed description of the device which simulates the transport of heat through geothermal heatpipes.

Full Text Available This work deal with evaluation of condenser temperature by experimental measurement, calculation and thermal visualization of cooling device working with a heatpipe technology. The referred device in the article is cooling device capable transfer high heat fluxes from electric elements to the surrounding. One from many things influenced the heat flux amount transferred from electronic elements through the cooling device to the surrounding is condenser construction, its capacity and option of heat removal. The work contain description, working principle and construction of cooling device. Experimental part describe the measuring method and mathematical calculation to condenser temperature evaluation of cooling device depending on the loaded heat of electronic components in range from 250 to 750 W. The mathematical calculation is based on physical phenomena of boiling, condensation and natural convection heat transfer. The results of experimental measurement and mathematical calculation are verified by thermal imagining of device condenser by IR camera.

Full Text Available LED development is accompanied by the need to ensure a constructive solution for the thermal conditions problem. For this purpose one can use pulsating heatpipes (PHP, that operate more efficiently after the start of heat carrier boiling. This article describes the physical representation and formula that allows determining the boiling point, which is a lower bound of the PHP effective operating range. It is shown that the main factors influencing the required heat flow are driving capillary pressure and velocity of the vapor bubble. The formula was obtained for the closed PHP made of the copper with water as a heat carrier. Information about this heat flux can be used for further design of cooling systems for heat-sensitive elements, such as LED for promising lighting devices.

Full Text Available Hard turning with minimal fluid application is a recently developed technique to alleviate the problem associated with cutting fluid. During this process, very small quantity of cutting fluid is applied as a narrow high velocity pulsing jet at the cutting zone. As the quantity of cutting fluid is very small, some auxiliary cooling of tool using heatpipe was attempted in the present work to enhance heat dissipation and thus improving cutting performance. Heatpipe was installed in vertical position in contact with the tool for extracting more heat from the tool. The influence of heatpipe cooling of tool on the cutting performance was analyzed by Taguchi's design of experiments. It was observed that the use of heatpipe in minimal fluid application reduced cutting temperature and tool wear to a maximum of 22% and 15%, respectively, in comparison with conventional hard turning with minimal fluid application without the aid of heatpipe. It appears that heatpipe can be successively employed as a mean of cooling the tool during hard turning with minimal fluid application.